All the numerical options, if not specified otherwise, accept a string
representing a number as input, which may be followed by one of the SI
unit prefixes, for example: ’K’, ’M’, or ’G’.

If ’i’ is appended to the SI unit prefix, the complete prefix will be
interpreted as a unit prefix for binary multiples, which are based on
powers of 1024 instead of powers of 1000. Appending ’B’ to the SI unit
prefix multiplies the value by 8. This allows using, for example:
’KB’, ’MiB’, ’G’ and ’B’ as number suffixes.

Options which do not take arguments are boolean options, and set the
corresponding value to true. They can be set to false by prefixing
the option name with "no". For example using "-nofoo"
will set the boolean option with name "foo" to false.

Some options are applied per-stream, e.g. bitrate or codec. Stream specifiers
are used to precisely specify which stream(s) a given option belongs to.

A stream specifier is a string generally appended to the option name and
separated from it by a colon. E.g. -codec:a:1 ac3 contains the
a:1 stream specifier, which matches the second audio stream. Therefore, it
would select the ac3 codec for the second audio stream.

A stream specifier can match several streams, so that the option is applied to all
of them. E.g. the stream specifier in -b:a 128k matches all audio
streams.

An empty stream specifier matches all streams. For example, -codec copy
or -codec: copy would copy all the streams without reencoding.

Possible forms of stream specifiers are:

stream_index

Matches the stream with this index. E.g. -threads:1 4 would set the
thread count for the second stream to 4.

stream_type[:stream_index]

stream_type is one of following: ’v’ or ’V’ for video, ’a’ for audio, ’s’
for subtitle, ’d’ for data, and ’t’ for attachments. ’v’ matches all video
streams, ’V’ only matches video streams which are not attached pictures, video
thumbnails or cover arts. If stream_index is given, then it matches
stream number stream_index of this type. Otherwise, it matches all
streams of this type.

p:program_id[:stream_index]

If stream_index is given, then it matches the stream with number stream_index
in the program with the id program_id. Otherwise, it matches all streams in the
program.

#stream_id or i:stream_id

Match the stream by stream id (e.g. PID in MPEG-TS container).

m:key[:value]

Matches streams with the metadata tag key having the specified value. If
value is not given, matches streams that contain the given tag with any
value.

u

Matches streams with usable configuration, the codec must be defined and the
essential information such as video dimension or audio sample rate must be present.

Note that in ffmpeg, matching by metadata will only work properly for
input files.

Print detailed information about the decoder named decoder_name. Use the
-decoders option to get a list of all decoders.

encoder=encoder_name

Print detailed information about the encoder named encoder_name. Use the
-encoders option to get a list of all encoders.

demuxer=demuxer_name

Print detailed information about the demuxer named demuxer_name. Use the
-formats option to get a list of all demuxers and muxers.

muxer=muxer_name

Print detailed information about the muxer named muxer_name. Use the
-formats option to get a list of all muxers and demuxers.

filter=filter_name

Print detailed information about the filter name filter_name. Use the
-filters option to get a list of all filters.

-version

Show version.

-formats

Show available formats (including devices).

-devices

Show available devices.

-codecs

Show all codecs known to libavcodec.

Note that the term ’codec’ is used throughout this documentation as a shortcut
for what is more correctly called a media bitstream format.

-decoders

Show available decoders.

-encoders

Show all available encoders.

-bsfs

Show available bitstream filters.

-protocols

Show available protocols.

-filters

Show available libavfilter filters.

-pix_fmts

Show available pixel formats.

-sample_fmts

Show available sample formats.

-layouts

Show channel names and standard channel layouts.

-colors

Show recognized color names.

-sources device[,opt1=val1[,opt2=val2]...]

Show autodetected sources of the intput device.
Some devices may provide system-dependent source names that cannot be autodetected.
The returned list cannot be assumed to be always complete.

ffmpeg -sources pulse,server=192.168.0.4

-sinks device[,opt1=val1[,opt2=val2]...]

Show autodetected sinks of the output device.
Some devices may provide system-dependent sink names that cannot be autodetected.
The returned list cannot be assumed to be always complete.

ffmpeg -sinks pulse,server=192.168.0.4

-loglevel [repeat+]loglevel | -v [repeat+]loglevel

Set the logging level used by the library.
Adding "repeat+" indicates that repeated log output should not be compressed
to the first line and the "Last message repeated n times" line will be
omitted. "repeat" can also be used alone.
If "repeat" is used alone, and with no prior loglevel set, the default
loglevel will be used. If multiple loglevel parameters are given, using
’repeat’ will not change the loglevel.
loglevel is a string or a number containing one of the following values:

‘quiet, -8’

Show nothing at all; be silent.

‘panic, 0’

Only show fatal errors which could lead the process to crash, such as
an assertion failure. This is not currently used for anything.

‘fatal, 8’

Only show fatal errors. These are errors after which the process absolutely
cannot continue.

‘error, 16’

Show all errors, including ones which can be recovered from.

‘warning, 24’

Show all warnings and errors. Any message related to possibly
incorrect or unexpected events will be shown.

‘info, 32’

Show informative messages during processing. This is in addition to
warnings and errors. This is the default value.

‘verbose, 40’

Same as info, except more verbose.

‘debug, 48’

Show everything, including debugging information.

‘trace, 56’

By default the program logs to stderr. If coloring is supported by the
terminal, colors are used to mark errors and warnings. Log coloring
can be disabled setting the environment variable
AV_LOG_FORCE_NOCOLOR or NO_COLOR, or can be forced setting
the environment variable AV_LOG_FORCE_COLOR.
The use of the environment variable NO_COLOR is deprecated and
will be dropped in a future FFmpeg version.

-report

Dump full command line and console output to a file named
program-YYYYMMDD-HHMMSS.log in the current
directory.
This file can be useful for bug reports.
It also implies -loglevel verbose.

Setting the environment variable FFREPORT to any value has the
same effect. If the value is a ’:’-separated key=value sequence, these
options will affect the report; option values must be escaped if they
contain special characters or the options delimiter ’:’ (see the
“Quoting and escaping” section in the ffmpeg-utils manual).

The following options are recognized:

file

set the file name to use for the report; %p is expanded to the name
of the program, %t is expanded to a timestamp, %% is expanded
to a plain %

level

set the log verbosity level using a numerical value (see -loglevel).

For example, to output a report to a file named ffreport.log
using a log level of 32 (alias for log level info):

FFREPORT=file=ffreport.log:level=32 ffmpeg -i input output

Errors in parsing the environment variable are not fatal, and will not
appear in the report.

-hide_banner

Suppress printing banner.

All FFmpeg tools will normally show a copyright notice, build options
and library versions. This option can be used to suppress printing
this information.

-cpuflags flags (global)

Allows setting and clearing cpu flags. This option is intended
for testing. Do not use it unless you know what you’re doing.

This option is used to benchmark all available OpenCL devices and print the
results. This option is only available when FFmpeg has been compiled with
--enable-opencl.

When FFmpeg is configured with --enable-opencl, the options for the
global OpenCL context are set via -opencl_options. See the
"OpenCL Options" section in the ffmpeg-utils manual for the complete list of
supported options. Amongst others, these options include the ability to select
a specific platform and device to run the OpenCL code on. By default, FFmpeg
will run on the first device of the first platform. While the options for the
global OpenCL context provide flexibility to the user in selecting the OpenCL
device of their choice, most users would probably want to select the fastest
OpenCL device for their system.

This option assists the selection of the most efficient configuration by
identifying the appropriate device for the user’s system. The built-in
benchmark is run on all the OpenCL devices and the performance is measured for
each device. The devices in the results list are sorted based on their
performance with the fastest device listed first. The user can subsequently
invoke ffmpeg using the device deemed most appropriate via
-opencl_options to obtain the best performance for the OpenCL
accelerated code.

Typical usage to use the fastest OpenCL device involve the following steps.

Run the command:

ffmpeg -opencl_bench

Note down the platform ID (pidx) and device ID (didx) of the first
i.e. fastest device in the list.
Select the platform and device using the command:

ffmpeg -opencl_options platform_idx=pidx:device_idx=didx ...

-opencl_options options (global)

Set OpenCL environment options. This option is only available when
FFmpeg has been compiled with --enable-opencl.

options must be a list of key=value option pairs
separated by ’:’. See the “OpenCL Options” section in the
ffmpeg-utils manual for the list of supported options.

Use SI prefixes for the displayed values.
Unless the "-byte_binary_prefix" option is used all the prefixes
are decimal.

-byte_binary_prefix

Force the use of binary prefixes for byte values.

-sexagesimal

Use sexagesimal format HH:MM:SS.MICROSECONDS for time values.

-pretty

Prettify the format of the displayed values, it corresponds to the
options "-unit -prefix -byte_binary_prefix -sexagesimal".

-of, -print_format writer_name[=writer_options]

Set the output printing format.

writer_name specifies the name of the writer, and
writer_options specifies the options to be passed to the writer.

For example for printing the output in JSON format, specify:

-print_format json

For more details on the available output printing formats, see the
Writers section below.

-sections

Print sections structure and section information, and exit. The output
is not meant to be parsed by a machine.

-select_streams stream_specifier

Select only the streams specified by stream_specifier. This
option affects only the options related to streams
(e.g. show_streams, show_packets, etc.).

For example to show only audio streams, you can use the command:

ffprobe -show_streams -select_streams a INPUT

To show only video packets belonging to the video stream with index 1:

ffprobe -show_packets -select_streams v:1 INPUT

-show_data

Show payload data, as a hexadecimal and ASCII dump. Coupled with
-show_packets, it will dump the packets’ data. Coupled with
-show_streams, it will dump the codec extradata.

The dump is printed as the "data" field. It may contain newlines.

-show_data_hash algorithm

Show a hash of payload data, for packets with -show_packets and for
codec extradata with -show_streams.

-show_error

Show information about the error found when trying to probe the input.

The error information is printed within a section with name "ERROR".

-show_format

Show information about the container format of the input multimedia
stream.

All the container format information is printed within a section with
name "FORMAT".

-show_format_entry name

Like -show_format, but only prints the specified entry of the
container format information, rather than all. This option may be given more
than once, then all specified entries will be shown.

This option is deprecated, use show_entries instead.

-show_entries section_entries

Set list of entries to show.

Entries are specified according to the following
syntax. section_entries contains a list of section entries
separated by :. Each section entry is composed by a section
name (or unique name), optionally followed by a list of entries local
to that section, separated by ,.

If section name is specified but is followed by no =, all
entries are printed to output, together with all the contained
sections. Otherwise only the entries specified in the local section
entries list are printed. In particular, if = is specified but
the list of local entries is empty, then no entries will be shown for
that section.

Note that the order of specification of the local section entries is
not honored in the output, and the usual display order will be
retained.

For example, to show only the index and type of each stream, and the PTS
time, duration time, and stream index of the packets, you can specify
the argument:

packet=pts_time,duration_time,stream_index : stream=index,codec_type

To show all the entries in the section "format", but only the codec
type in the section "stream", specify the argument:

format : stream=codec_type

To show all the tags in the stream and format sections:

stream_tags : format_tags

To show only the title tag (if available) in the stream
sections:

stream_tags=title

-show_packets

Show information about each packet contained in the input multimedia
stream.

The information for each single packet is printed within a dedicated
section with name "PACKET".

-show_frames

Show information about each frame and subtitle contained in the input
multimedia stream.

The information for each single frame is printed within a dedicated
section with name "FRAME" or "SUBTITLE".

-show_streams

Show information about each media stream contained in the input
multimedia stream.

Each media stream information is printed within a dedicated section
with name "STREAM".

-show_programs

Show information about programs and their streams contained in the input
multimedia stream.

Each media stream information is printed within a dedicated section
with name "PROGRAM_STREAM".

-show_chapters

Show information about chapters stored in the format.

Each chapter is printed within a dedicated section with name "CHAPTER".

-count_frames

Count the number of frames per stream and report it in the
corresponding stream section.

-count_packets

Count the number of packets per stream and report it in the
corresponding stream section.

-read_intervals read_intervals

Read only the specified intervals. read_intervals must be a
sequence of interval specifications separated by ",".
ffprobe will seek to the interval starting point, and will
continue reading from that.

Each interval is specified by two optional parts, separated by "%".

The first part specifies the interval start position. It is
interpreted as an absolute position, or as a relative offset from the
current position if it is preceded by the "+" character. If this first
part is not specified, no seeking will be performed when reading this
interval.

The second part specifies the interval end position. It is interpreted
as an absolute position, or as a relative offset from the current
position if it is preceded by the "+" character. If the offset
specification starts with "#", it is interpreted as the number of
packets to read (not including the flushing packets) from the interval
start. If no second part is specified, the program will read until the
end of the input.

Note that seeking is not accurate, thus the actual interval start
point may be different from the specified position. Also, when an
interval duration is specified, the absolute end time will be computed
by adding the duration to the interval start point found by seeking
the file, rather than to the specified start value.

Seek to time 10, read packets until 20 seconds after the found seek
point, then seek to position 01:30 (1 minute and thirty
seconds) and read packets until position 01:45.

10%+20,01:30%01:45

Read only 42 packets after seeking to position 01:23:

01:23%+#42

Read only the first 20 seconds from the start:

%+20

Read from the start until position 02:30:

%02:30

-show_private_data, -private

Show private data, that is data depending on the format of the
particular shown element.
This option is enabled by default, but you may need to disable it
for specific uses, for example when creating XSD-compliant XML output.

-show_program_version

Show information related to program version.

Version information is printed within a section with name
"PROGRAM_VERSION".

-show_library_versions

Show information related to library versions.

Version information for each library is printed within a section with
name "LIBRARY_VERSION".

-show_versions

Show information related to program and library versions. This is the
equivalent of setting both -show_program_version and
-show_library_versions options.

-show_pixel_formats

Show information about all pixel formats supported by FFmpeg.

Pixel format information for each format is printed within a section
with name "PIXEL_FORMAT".

-bitexact

Force bitexact output, useful to produce output which is not dependent
on the specific build.

The csv writer is equivalent to compact, but supports
different defaults.

Each section is printed on a single line.
If no option is specifid, the output has the form:

section|key1=val1| ... |keyN=valN

Metadata tags are printed in the corresponding "format" or "stream"
section. A metadata tag key, if printed, is prefixed by the string
"tag:".

The description of the accepted options follows.

item_sep, s

Specify the character to use for separating fields in the output line.
It must be a single printable character, it is "|" by default ("," for
the csv writer).

nokey, nk

If set to 1 specify not to print the key of each field. Its default
value is 0 (1 for the csv writer).

escape, e

Set the escape mode to use, default to "c" ("csv" for the csv
writer).

It can assume one of the following values:

c

Perform C-like escaping. Strings containing a newline (‘\n’), carriage
return (‘\r’), a tab (‘\t’), a form feed (‘\f’), the escaping
character (‘\’) or the item separator character SEP are escaped
using C-like fashioned escaping, so that a newline is converted to the
sequence ‘\n’, a carriage return to ‘\r’, ‘\’ to ‘\\’ and
the separator SEP is converted to ‘\SEP’.

csv

Perform CSV-like escaping, as described in RFC4180. Strings
containing a newline (‘\n’), a carriage return (‘\r’), a double quote
(‘"’), or SEP are enclosed in double-quotes.

none

Perform no escaping.

print_section, p

Print the section name at the begin of each line if the value is
1, disable it with value set to 0. Default value is
1.

A free-form output where each line contains an explicit key=value, such as
"streams.stream.3.tags.foo=bar". The output is shell escaped, so it can be
directly embedded in sh scripts as long as the separator character is an
alphanumeric character or an underscore (see sep_char option).

The description of the accepted options follows.

sep_char, s

Separator character used to separate the chapter, the section name, IDs and
potential tags in the printed field key.

Default value is ‘.’.

hierarchical, h

Specify if the section name specification should be hierarchical. If
set to 1, and if there is more than one section in the current
chapter, the section name will be prefixed by the name of the
chapter. A value of 0 will disable this behavior.

This writer accepts options as a list of key=value pairs,
separated by ‘:’.

The description of the accepted options follows.

hierarchical, h

Specify if the section name specification should be hierarchical. If
set to 1, and if there is more than one section in the current
chapter, the section name will be prefixed by the name of the
chapter. A value of 0 will disable this behavior.

FFmpeg adopts the following quoting and escaping mechanism, unless
explicitly specified. The following rules are applied:

‘'’ and ‘\’ are special characters (respectively used for
quoting and escaping). In addition to them, there might be other
special characters depending on the specific syntax where the escaping
and quoting are employed.

A special character is escaped by prefixing it with a ‘\’.

All characters enclosed between ‘''’ are included literally in the
parsed string. The quote character ‘'’ itself cannot be quoted,
so you may need to close the quote and escape it.

Leading and trailing whitespaces, unless escaped or quoted, are
removed from the parsed string.

Note that you may need to add a second level of escaping when using
the command line or a script, which depends on the syntax of the
adopted shell language.

The function av_get_token defined in
libavutil/avstring.h can be used to parse a token quoted or
escaped according to the rules defined above.

The tool tools/ffescape in the FFmpeg source tree can be used
to automatically quote or escape a string in a script.

Specify the frame rate of a video, expressed as the number of frames
generated per second. It has to be a string in the format
frame_rate_num/frame_rate_den, an integer number, a float
number or a valid video frame rate abbreviation.

It can be the name of a color as defined below (case insensitive match) or a
[0x|#]RRGGBB[AA] sequence, possibly followed by @ and a string
representing the alpha component.

The alpha component may be a string composed by "0x" followed by an
hexadecimal number or a decimal number between 0.0 and 1.0, which
represents the opacity value (‘0x00’ or ‘0.0’ means completely
transparent, ‘0xff’ or ‘1.0’ completely opaque). If the alpha
component is not specified then ‘0xff’ is assumed.

a number of channels, in decimal, optionally followed by ’c’, yielding
the default channel layout for that number of channels (see the
function av_get_default_channel_layout)

a channel layout mask, in hexadecimal starting with "0x" (see the
AV_CH_* macros in libavutil/channel_layout.h.

Starting from libavutil version 53 the trailing character "c" to
specify a number of channels will be required, while a channel layout
mask could also be specified as a decimal number (if and only if not
followed by "c").

See also the function av_get_channel_layout defined in
libavutil/channel_layout.h.

Return the greatest common divisor of x and y. If both x and
y are 0 or either or both are less than zero then behavior is undefined.

gt(x, y)

Return 1 if x is greater than y, 0 otherwise.

gte(x, y)

Return 1 if x is greater than or equal to y, 0 otherwise.

hypot(x, y)

This function is similar to the C function with the same name; it returns
"sqrt(x*x + y*y)", the length of the hypotenuse of a
right triangle with sides of length x and y, or the distance of the
point (x, y) from the origin.

if(x, y)

Evaluate x, and if the result is non-zero return the result of
the evaluation of y, return 0 otherwise.

if(x, y, z)

Evaluate x, and if the result is non-zero return the evaluation
result of y, otherwise the evaluation result of z.

ifnot(x, y)

Evaluate x, and if the result is zero return the result of the
evaluation of y, return 0 otherwise.

ifnot(x, y, z)

Evaluate x, and if the result is zero return the evaluation
result of y, otherwise the evaluation result of z.

isinf(x)

Return 1.0 if x is +/-INFINITY, 0.0 otherwise.

isnan(x)

Return 1.0 if x is NAN, 0.0 otherwise.

ld(var)

Load the value of the internal variable with number
var, which was previously stored with st(var, expr).
The function returns the loaded value.

log(x)

Compute natural logarithm of x.

lt(x, y)

Return 1 if x is lesser than y, 0 otherwise.

lte(x, y)

Return 1 if x is lesser than or equal to y, 0 otherwise.

max(x, y)

Return the maximum between x and y.

min(x, y)

Return the minimum between x and y.

mod(x, y)

Compute the remainder of division of x by y.

not(expr)

Return 1.0 if expr is zero, 0.0 otherwise.

pow(x, y)

Compute the power of x elevated y, it is equivalent to
"(x)^(y)".

print(t)

print(t, l)

Print the value of expression t with loglevel l. If
l is not specified then a default log level is used.
Returns the value of the expression printed.

Prints t with loglevel l

random(x)

Return a pseudo random value between 0.0 and 1.0. x is the index of the
internal variable which will be used to save the seed/state.

root(expr, max)

Find an input value for which the function represented by expr
with argument ld(0) is 0 in the interval 0..max.

The expression in expr must denote a continuous function or the
result is undefined.

ld(0) is used to represent the function input value, which means
that the given expression will be evaluated multiple times with
various input values that the expression can access through
ld(0). When the expression evaluates to 0 then the
corresponding input value will be returned.

sin(x)

Compute sine of x.

sinh(x)

Compute hyperbolic sine of x.

sqrt(expr)

Compute the square root of expr. This is equivalent to
"(expr)^.5".

squish(x)

Compute expression 1/(1 + exp(4*x)).

st(var, expr)

Store the value of the expression expr in an internal
variable. var specifies the number of the variable where to
store the value, and it is a value ranging from 0 to 9. The function
returns the value stored in the internal variable.
Note, Variables are currently not shared between expressions.

tan(x)

Compute tangent of x.

tanh(x)

Compute hyperbolic tangent of x.

taylor(expr, x)

taylor(expr, x, id)

Evaluate a Taylor series at x, given an expression representing
the ld(id)-th derivative of a function at 0.

When the series does not converge the result is undefined.

ld(id) is used to represent the derivative order in expr,
which means that the given expression will be evaluated multiple times
with various input values that the expression can access through
ld(id). If id is not specified then 0 is assumed.

Note, when you have the derivatives at y instead of 0,
taylor(expr, x-y) can be used.

time(0)

Return the current (wallclock) time in seconds.

trunc(expr)

Round the value of expression expr towards zero to the nearest
integer. For example, "trunc(-1.5)" is "-1.0".

while(cond, expr)

Evaluate expression expr while the expression cond is
non-zero, and returns the value of the last expr evaluation, or
NAN if cond was always false.

The following constants are available:

PI

area of the unit disc, approximately 3.14

E

exp(1) (Euler’s number), approximately 2.718

PHI

golden ratio (1+sqrt(5))/2, approximately 1.618

Assuming that an expression is considered "true" if it has a non-zero
value, note that:

* works like AND

+ works like OR

For example the construct:

if (A AND B) then C

is equivalent to:

if(A*B, C)

In your C code, you can extend the list of unary and binary functions,
and define recognized constants, so that they are available for your
expressions.

The evaluator also recognizes the International System unit prefixes.
If ’i’ is appended after the prefix, binary prefixes are used, which
are based on powers of 1024 instead of powers of 1000.
The ’B’ postfix multiplies the value by 8, and can be appended after a
unit prefix or used alone. This allows using for example ’KB’, ’MiB’,
’G’ and ’B’ as number postfix.

The list of available International System prefixes follows, with
indication of the corresponding powers of 10 and of 2.

libavcodec provides some generic global options, which can be set on
all the encoders and decoders. In addition each codec may support
so-called private options, which are specific for a given codec.

Sometimes, a global option may only affect a specific kind of codec,
and may be nonsensical or ignored by another, so you need to be aware
of the meaning of the specified options. Also some options are
meant only for decoding or encoding.

Options may be set by specifying -optionvalue in the
FFmpeg tools, or by setting the value explicitly in the
AVCodecContext options or using the libavutil/opt.h API
for programmatic use.

The list of supported options follow:

b integer (encoding,audio,video)

Set bitrate in bits/s. Default value is 200K.

ab integer (encoding,audio)

Set audio bitrate (in bits/s). Default value is 128K.

bt integer (encoding,video)

Set video bitrate tolerance (in bits/s). In 1-pass mode, bitrate
tolerance specifies how far ratecontrol is willing to deviate from the
target average bitrate value. This is not related to min/max
bitrate. Lowering tolerance too much has an adverse effect on quality.

flags flags (decoding/encoding,audio,video,subtitles)

Set generic flags.

Possible values:

‘mv4’

Use four motion vector by macroblock (mpeg4).

‘qpel’

Use 1/4 pel motion compensation.

‘loop’

Use loop filter.

‘qscale’

Use fixed qscale.

‘gmc’

Use gmc.

‘mv0’

Always try a mb with mv=<0,0>.

‘input_preserved’

‘pass1’

Use internal 2pass ratecontrol in first pass mode.

‘pass2’

Use internal 2pass ratecontrol in second pass mode.

‘gray’

Only decode/encode grayscale.

‘emu_edge’

Do not draw edges.

‘psnr’

Set error[?] variables during encoding.

‘truncated’

‘naq’

Normalize adaptive quantization.

‘ildct’

Use interlaced DCT.

‘low_delay’

Force low delay.

‘global_header’

Place global headers in extradata instead of every keyframe.

‘bitexact’

Only write platform-, build- and time-independent data. (except (I)DCT).
This ensures that file and data checksums are reproducible and match between
platforms. Its primary use is for regression testing.

‘aic’

Apply H263 advanced intra coding / mpeg4 ac prediction.

‘cbp’

Deprecated, use mpegvideo private options instead.

‘qprd’

Deprecated, use mpegvideo private options instead.

‘ilme’

Apply interlaced motion estimation.

‘cgop’

Use closed gop.

me_method integer (encoding,video)

Set motion estimation method.

Possible values:

‘zero’

zero motion estimation (fastest)

‘full’

full motion estimation (slowest)

‘epzs’

EPZS motion estimation (default)

‘esa’

esa motion estimation (alias for full)

‘tesa’

tesa motion estimation

‘dia’

dia motion estimation (alias for epzs)

‘log’

log motion estimation

‘phods’

phods motion estimation

‘x1’

X1 motion estimation

‘hex’

hex motion estimation

‘umh’

umh motion estimation

‘iter’

iter motion estimation

extradata_size integer

Set extradata size.

time_base rational number

Set codec time base.

It is the fundamental unit of time (in seconds) in terms of which
frame timestamps are represented. For fixed-fps content, timebase
should be 1 / frame_rate and timestamp increments should be
identically 1.

g integer (encoding,video)

Set the group of picture (GOP) size. Default value is 12.

ar integer (decoding/encoding,audio)

Set audio sampling rate (in Hz).

ac integer (decoding/encoding,audio)

Set number of audio channels.

cutoff integer (encoding,audio)

Set cutoff bandwidth.

frame_size integer (encoding,audio)

Set audio frame size.

Each submitted frame except the last must contain exactly frame_size
samples per channel. May be 0 when the codec has
CODEC_CAP_VARIABLE_FRAME_SIZE set, in that case the frame size is not
restricted. It is set by some decoders to indicate constant frame
size.

frame_number integer

Set the frame number.

delay integer

qcomp float (encoding,video)

Set video quantizer scale compression (VBR). It is used as a constant
in the ratecontrol equation. Recommended range for default rc_eq:
0.0-1.0.

qblur float (encoding,video)

Set video quantizer scale blur (VBR).

qmin integer (encoding,video)

Set min video quantizer scale (VBR). Must be included between -1 and
69, default value is 2.

qmax integer (encoding,video)

Set max video quantizer scale (VBR). Must be included between -1 and
1024, default value is 31.

qdiff integer (encoding,video)

Set max difference between the quantizer scale (VBR).

bf integer (encoding,video)

Set max number of B frames between non-B-frames.

Must be an integer between -1 and 16. 0 means that B-frames are
disabled. If a value of -1 is used, it will choose an automatic value
depending on the encoder.

Default value is 0.

b_qfactor float (encoding,video)

Set qp factor between P and B frames.

rc_strategy integer (encoding,video)

Set ratecontrol method.

b_strategy integer (encoding,video)

Set strategy to choose between I/P/B-frames.

ps integer (encoding,video)

Set RTP payload size in bytes.

mv_bits integer

header_bits integer

i_tex_bits integer

p_tex_bits integer

i_count integer

p_count integer

skip_count integer

misc_bits integer

frame_bits integer

codec_tag integer

bug flags (decoding,video)

Workaround not auto detected encoder bugs.

Possible values:

‘autodetect’

‘old_msmpeg4’

some old lavc generated msmpeg4v3 files (no autodetection)

‘xvid_ilace’

Xvid interlacing bug (autodetected if fourcc==XVIX)

‘ump4’

(autodetected if fourcc==UMP4)

‘no_padding’

padding bug (autodetected)

‘amv’

‘ac_vlc’

illegal vlc bug (autodetected per fourcc)

‘qpel_chroma’

‘std_qpel’

old standard qpel (autodetected per fourcc/version)

‘qpel_chroma2’

‘direct_blocksize’

direct-qpel-blocksize bug (autodetected per fourcc/version)

‘edge’

edge padding bug (autodetected per fourcc/version)

‘hpel_chroma’

‘dc_clip’

‘ms’

Workaround various bugs in microsoft broken decoders.

‘trunc’

trancated frames

lelim integer (encoding,video)

Set single coefficient elimination threshold for luminance (negative
values also consider DC coefficient).

celim integer (encoding,video)

Set single coefficient elimination threshold for chrominance (negative
values also consider dc coefficient)

strict integer (decoding/encoding,audio,video)

Specify how strictly to follow the standards.

Possible values:

‘very’

strictly conform to an older more strict version of the spec or reference software

‘strict’

strictly conform to all the things in the spec no matter what consequences

‘normal’

‘unofficial’

allow unofficial extensions

‘experimental’

allow non standardized experimental things, experimental
(unfinished/work in progress/not well tested) decoders and encoders.
Note: experimental decoders can pose a security risk, do not use this for
decoding untrusted input.

b_qoffset float (encoding,video)

Set QP offset between P and B frames.

err_detect flags (decoding,audio,video)

Set error detection flags.

Possible values:

‘crccheck’

verify embedded CRCs

‘bitstream’

detect bitstream specification deviations

‘buffer’

detect improper bitstream length

‘explode’

abort decoding on minor error detection

‘ignore_err’

ignore decoding errors, and continue decoding.
This is useful if you want to analyze the content of a video and thus want
everything to be decoded no matter what. This option will not result in a video
that is pleasing to watch in case of errors.

‘careful’

consider things that violate the spec and have not been seen in the wild as errors

‘compliant’

consider all spec non compliancies as errors

‘aggressive’

consider things that a sane encoder should not do as an error

has_b_frames integer

block_align integer

mpeg_quant integer (encoding,video)

Use MPEG quantizers instead of H.263.

qsquish float (encoding,video)

How to keep quantizer between qmin and qmax (0 = clip, 1 = use
differentiable function).

Set min bitrate tolerance (in bits/s). Most useful in setting up a CBR
encode. It is of little use elsewise.

bufsize integer (encoding,audio,video)

Set ratecontrol buffer size (in bits).

rc_buf_aggressivity float (encoding,video)

Currently useless.

i_qfactor float (encoding,video)

Set QP factor between P and I frames.

i_qoffset float (encoding,video)

Set QP offset between P and I frames.

rc_init_cplx float (encoding,video)

Set initial complexity for 1-pass encoding.

dct integer (encoding,video)

Set DCT algorithm.

Possible values:

‘auto’

autoselect a good one (default)

‘fastint’

fast integer

‘int’

accurate integer

‘mmx’

‘altivec’

‘faan’

floating point AAN DCT

lumi_mask float (encoding,video)

Compress bright areas stronger than medium ones.

tcplx_mask float (encoding,video)

Set temporal complexity masking.

scplx_mask float (encoding,video)

Set spatial complexity masking.

p_mask float (encoding,video)

Set inter masking.

dark_mask float (encoding,video)

Compress dark areas stronger than medium ones.

idct integer (decoding/encoding,video)

Select IDCT implementation.

Possible values:

‘auto’

‘int’

‘simple’

‘simplemmx’

‘simpleauto’

Automatically pick a IDCT compatible with the simple one

‘arm’

‘altivec’

‘sh4’

‘simplearm’

‘simplearmv5te’

‘simplearmv6’

‘simpleneon’

‘simplealpha’

‘ipp’

‘xvidmmx’

‘faani’

floating point AAN IDCT

slice_count integer

ec flags (decoding,video)

Set error concealment strategy.

Possible values:

‘guess_mvs’

iterative motion vector (MV) search (slow)

‘deblock’

use strong deblock filter for damaged MBs

‘favor_inter’

favor predicting from the previous frame instead of the current

bits_per_coded_sample integer

pred integer (encoding,video)

Set prediction method.

Possible values:

‘left’

‘plane’

‘median’

aspect rational number (encoding,video)

Set sample aspect ratio.

sar rational number (encoding,video)

Set sample aspect ratio. Alias to aspect.

debug flags (decoding/encoding,audio,video,subtitles)

Print specific debug info.

Possible values:

‘pict’

picture info

‘rc’

rate control

‘bitstream’

‘mb_type’

macroblock (MB) type

‘qp’

per-block quantization parameter (QP)

‘mv’

motion vector

‘dct_coeff’

‘green_metadata’

display complexity metadata for the upcoming frame, GoP or for a given duration.

‘skip’

‘startcode’

‘pts’

‘er’

error recognition

‘mmco’

memory management control operations (H.264)

‘bugs’

‘vis_qp’

visualize quantization parameter (QP), lower QP are tinted greener

‘vis_mb_type’

visualize block types

‘buffers’

picture buffer allocations

‘thread_ops’

threading operations

‘nomc’

skip motion compensation

vismv integer (decoding,video)

Visualize motion vectors (MVs).

This option is deprecated, see the codecview filter instead.

Possible values:

‘pf’

forward predicted MVs of P-frames

‘bf’

forward predicted MVs of B-frames

‘bb’

backward predicted MVs of B-frames

cmp integer (encoding,video)

Set full pel me compare function.

Possible values:

‘sad’

sum of absolute differences, fast (default)

‘sse’

sum of squared errors

‘satd’

sum of absolute Hadamard transformed differences

‘dct’

sum of absolute DCT transformed differences

‘psnr’

sum of squared quantization errors (avoid, low quality)

‘bit’

number of bits needed for the block

‘rd’

rate distortion optimal, slow

‘zero’

0

‘vsad’

sum of absolute vertical differences

‘vsse’

sum of squared vertical differences

‘nsse’

noise preserving sum of squared differences

‘w53’

5/3 wavelet, only used in snow

‘w97’

9/7 wavelet, only used in snow

‘dctmax’

‘chroma’

subcmp integer (encoding,video)

Set sub pel me compare function.

Possible values:

‘sad’

sum of absolute differences, fast (default)

‘sse’

sum of squared errors

‘satd’

sum of absolute Hadamard transformed differences

‘dct’

sum of absolute DCT transformed differences

‘psnr’

sum of squared quantization errors (avoid, low quality)

‘bit’

number of bits needed for the block

‘rd’

rate distortion optimal, slow

‘zero’

0

‘vsad’

sum of absolute vertical differences

‘vsse’

sum of squared vertical differences

‘nsse’

noise preserving sum of squared differences

‘w53’

5/3 wavelet, only used in snow

‘w97’

9/7 wavelet, only used in snow

‘dctmax’

‘chroma’

mbcmp integer (encoding,video)

Set macroblock compare function.

Possible values:

‘sad’

sum of absolute differences, fast (default)

‘sse’

sum of squared errors

‘satd’

sum of absolute Hadamard transformed differences

‘dct’

sum of absolute DCT transformed differences

‘psnr’

sum of squared quantization errors (avoid, low quality)

‘bit’

number of bits needed for the block

‘rd’

rate distortion optimal, slow

‘zero’

0

‘vsad’

sum of absolute vertical differences

‘vsse’

sum of squared vertical differences

‘nsse’

noise preserving sum of squared differences

‘w53’

5/3 wavelet, only used in snow

‘w97’

9/7 wavelet, only used in snow

‘dctmax’

‘chroma’

ildctcmp integer (encoding,video)

Set interlaced dct compare function.

Possible values:

‘sad’

sum of absolute differences, fast (default)

‘sse’

sum of squared errors

‘satd’

sum of absolute Hadamard transformed differences

‘dct’

sum of absolute DCT transformed differences

‘psnr’

sum of squared quantization errors (avoid, low quality)

‘bit’

number of bits needed for the block

‘rd’

rate distortion optimal, slow

‘zero’

0

‘vsad’

sum of absolute vertical differences

‘vsse’

sum of squared vertical differences

‘nsse’

noise preserving sum of squared differences

‘w53’

5/3 wavelet, only used in snow

‘w97’

9/7 wavelet, only used in snow

‘dctmax’

‘chroma’

dia_size integer (encoding,video)

Set diamond type & size for motion estimation.

last_pred integer (encoding,video)

Set amount of motion predictors from the previous frame.

preme integer (encoding,video)

Set pre motion estimation.

precmp integer (encoding,video)

Set pre motion estimation compare function.

Possible values:

‘sad’

sum of absolute differences, fast (default)

‘sse’

sum of squared errors

‘satd’

sum of absolute Hadamard transformed differences

‘dct’

sum of absolute DCT transformed differences

‘psnr’

sum of squared quantization errors (avoid, low quality)

‘bit’

number of bits needed for the block

‘rd’

rate distortion optimal, slow

‘zero’

0

‘vsad’

sum of absolute vertical differences

‘vsse’

sum of squared vertical differences

‘nsse’

noise preserving sum of squared differences

‘w53’

5/3 wavelet, only used in snow

‘w97’

9/7 wavelet, only used in snow

‘dctmax’

‘chroma’

pre_dia_size integer (encoding,video)

Set diamond type & size for motion estimation pre-pass.

subq integer (encoding,video)

Set sub pel motion estimation quality.

dtg_active_format integer

me_range integer (encoding,video)

Set limit motion vectors range (1023 for DivX player).

ibias integer (encoding,video)

Set intra quant bias.

pbias integer (encoding,video)

Set inter quant bias.

color_table_id integer

global_quality integer (encoding,audio,video)

coder integer (encoding,video)

Possible values:

‘vlc’

variable length coder / huffman coder

‘ac’

arithmetic coder

‘raw’

raw (no encoding)

‘rle’

run-length coder

‘deflate’

deflate-based coder

context integer (encoding,video)

Set context model.

slice_flags integer

xvmc_acceleration integer

mbd integer (encoding,video)

Set macroblock decision algorithm (high quality mode).

Possible values:

‘simple’

use mbcmp (default)

‘bits’

use fewest bits

‘rd’

use best rate distortion

stream_codec_tag integer

sc_threshold integer (encoding,video)

Set scene change threshold.

lmin integer (encoding,video)

Set min lagrange factor (VBR).

lmax integer (encoding,video)

Set max lagrange factor (VBR).

nr integer (encoding,video)

Set noise reduction.

rc_init_occupancy integer (encoding,video)

Set number of bits which should be loaded into the rc buffer before
decoding starts.

flags2 flags (decoding/encoding,audio,video)

Possible values:

‘fast’

Allow non spec compliant speedup tricks.

‘sgop’

Deprecated, use mpegvideo private options instead.

‘noout’

Skip bitstream encoding.

‘ignorecrop’

Ignore cropping information from sps.

‘local_header’

Place global headers at every keyframe instead of in extradata.

‘chunks’

Frame data might be split into multiple chunks.

‘showall’

Show all frames before the first keyframe.

‘skiprd’

Deprecated, use mpegvideo private options instead.

‘export_mvs’

Export motion vectors into frame side-data (see AV_FRAME_DATA_MOTION_VECTORS)
for codecs that support it. See also doc/examples/export_mvs.c.

error integer (encoding,video)

qns integer (encoding,video)

Deprecated, use mpegvideo private options instead.

threads integer (decoding/encoding,video)

Set the number of threads to be used, in case the selected codec
implementation supports multi-threading.

Possible values:

‘auto, 0’

automatically select the number of threads to set

Default value is ‘auto’.

me_threshold integer (encoding,video)

Set motion estimation threshold.

mb_threshold integer (encoding,video)

Set macroblock threshold.

dc integer (encoding,video)

Set intra_dc_precision.

nssew integer (encoding,video)

Set nsse weight.

skip_top integer (decoding,video)

Set number of macroblock rows at the top which are skipped.

skip_bottom integer (decoding,video)

Set number of macroblock rows at the bottom which are skipped.

profile integer (encoding,audio,video)

Possible values:

‘unknown’

‘aac_main’

‘aac_low’

‘aac_ssr’

‘aac_ltp’

‘aac_he’

‘aac_he_v2’

‘aac_ld’

‘aac_eld’

‘mpeg2_aac_low’

‘mpeg2_aac_he’

‘mpeg4_sp’

‘mpeg4_core’

‘mpeg4_main’

‘mpeg4_asp’

‘dts’

‘dts_es’

‘dts_96_24’

‘dts_hd_hra’

‘dts_hd_ma’

level integer (encoding,audio,video)

Possible values:

‘unknown’

lowres integer (decoding,audio,video)

Decode at 1= 1/2, 2=1/4, 3=1/8 resolutions.

skip_threshold integer (encoding,video)

Set frame skip threshold.

skip_factor integer (encoding,video)

Set frame skip factor.

skip_exp integer (encoding,video)

Set frame skip exponent.
Negative values behave identical to the corresponding positive ones, except
that the score is normalized.
Positive values exist primarily for compatibility reasons and are not so useful.

skipcmp integer (encoding,video)

Set frame skip compare function.

Possible values:

‘sad’

sum of absolute differences, fast (default)

‘sse’

sum of squared errors

‘satd’

sum of absolute Hadamard transformed differences

‘dct’

sum of absolute DCT transformed differences

‘psnr’

sum of squared quantization errors (avoid, low quality)

‘bit’

number of bits needed for the block

‘rd’

rate distortion optimal, slow

‘zero’

0

‘vsad’

sum of absolute vertical differences

‘vsse’

sum of squared vertical differences

‘nsse’

noise preserving sum of squared differences

‘w53’

5/3 wavelet, only used in snow

‘w97’

9/7 wavelet, only used in snow

‘dctmax’

‘chroma’

border_mask float (encoding,video)

Increase the quantizer for macroblocks close to borders.

mblmin integer (encoding,video)

Set min macroblock lagrange factor (VBR).

mblmax integer (encoding,video)

Set max macroblock lagrange factor (VBR).

mepc integer (encoding,video)

Set motion estimation bitrate penalty compensation (1.0 = 256).

skip_loop_filter integer (decoding,video)

skip_idct integer (decoding,video)

skip_frame integer (decoding,video)

Make decoder discard processing depending on the frame type selected
by the option value.

Decoders are configured elements in FFmpeg which allow the decoding of
multimedia streams.

When you configure your FFmpeg build, all the supported native decoders
are enabled by default. Decoders requiring an external library must be enabled
manually via the corresponding --enable-lib option. You can list all
available decoders using the configure option --list-decoders.

You can disable all the decoders with the configure option
--disable-decoders and selectively enable / disable single decoders
with the options --enable-decoder=DECODER /
--disable-decoder=DECODER.

The option -decoders of the ff* tools will display the list of
enabled decoders.

The lavc FLAC encoder used to produce buggy streams with high lpc values
(like the default value). This option makes it possible to decode such streams
correctly by using lavc’s old buggy lpc logic for decoding.

libcelt allows libavcodec to decode the Xiph CELT ultra-low delay audio codec.
Requires the presence of the libcelt headers and library during configuration.
You need to explicitly configure the build with --enable-libcelt.

libgsm allows libavcodec to decode the GSM full rate audio codec. Requires
the presence of the libgsm headers and library during configuration. You need
to explicitly configure the build with --enable-libgsm.

This decoder supports both the ordinary GSM and the Microsoft variant.

libilbc allows libavcodec to decode the Internet Low Bitrate Codec (iLBC)
audio codec. Requires the presence of the libilbc headers and library during
configuration. You need to explicitly configure the build with
--enable-libilbc.

libopencore-amrnb allows libavcodec to decode the Adaptive Multi-Rate
Narrowband audio codec. Using it requires the presence of the
libopencore-amrnb headers and library during configuration. You need to
explicitly configure the build with --enable-libopencore-amrnb.

An FFmpeg native decoder for AMR-NB exists, so users can decode AMR-NB
without this library.

libopencore-amrwb allows libavcodec to decode the Adaptive Multi-Rate
Wideband audio codec. Using it requires the presence of the
libopencore-amrwb headers and library during configuration. You need to
explicitly configure the build with --enable-libopencore-amrwb.

An FFmpeg native decoder for AMR-WB exists, so users can decode AMR-WB
without this library.

libopus allows libavcodec to decode the Opus Interactive Audio Codec.
Requires the presence of the libopus headers and library during
configuration. You need to explicitly configure the build with
--enable-libopus.

An FFmpeg native decoder for Opus exists, so users can decode Opus
without this library.

Specify the global palette used by the bitmaps. When stored in VobSub, the
palette is normally specified in the index file; in Matroska, the palette is
stored in the codec extra-data in the same format as in VobSub. In DVDs, the
palette is stored in the IFO file, and therefore not available when reading
from dumped VOB files.

Libzvbi allows libavcodec to decode DVB teletext pages and DVB teletext
subtitles. Requires the presence of the libzvbi headers and library during
configuration. You need to explicitly configure the build with
--enable-libzvbi.

List of teletext page numbers to decode. You may use the special * string to
match all pages. Pages that do not match the specified list are dropped.
Default value is *.

txt_chop_top

Discards the top teletext line. Default value is 1.

txt_format

Specifies the format of the decoded subtitles. The teletext decoder is capable
of decoding the teletext pages to bitmaps or to simple text, you should use
"bitmap" for teletext pages, because certain graphics and colors cannot be
expressed in simple text. You might use "text" for teletext based subtitles if
your application can handle simple text based subtitles. Default value is
bitmap.

txt_left

X offset of generated bitmaps, default is 0.

txt_top

Y offset of generated bitmaps, default is 0.

txt_chop_spaces

Chops leading and trailing spaces and removes empty lines from the generated
text. This option is useful for teletext based subtitles where empty spaces may
be present at the start or at the end of the lines or empty lines may be
present between the subtitle lines because of double-sized teletext charactes.
Default value is 1.

txt_duration

Sets the display duration of the decoded teletext pages or subtitles in
milliseconds. Default value is 30000 which is 30 seconds.

Sets the opacity (0-255) of the teletext background. If
txt_transparent is not set, it only affects characters between a start
box and an end box, typically subtitles. Default value is 0 if
txt_transparent is set, 255 otherwise.

When you configure your FFmpeg build, all the supported bitstream
filters are enabled by default. You can list all available ones using
the configure option --list-bsfs.

You can disable all the bitstream filters using the configure option
--disable-bsfs, and selectively enable any bitstream filter using
the option --enable-bsf=BSF, or you can disable a particular
bitstream filter using the option --disable-bsf=BSF.

The option -bsfs of the ff* tools will display the list of
all the supported bitstream filters included in your build.

The ff* tools have a -bsf option applied per stream, taking a
comma-separated list of filters, whose parameters follow the filter
name after a ’=’.

This filter creates an MPEG-4 AudioSpecificConfig from an MPEG-2/4
ADTS header and removes the ADTS header.

This filter is required for example when copying an AAC stream from a
raw ADTS AAC or an MPEG-TS container to MP4A-LATM, to an FLV file, or
to MOV/MP4 files and related formats such as 3GP or M4A. Please note
that it is auto-inserted for MP4A-LATM and MOV/MP4 and related formats.

The additional argument specifies which packets should be filtered.
It accepts the values:

‘a’

add extradata to all key packets, but only if local_header is
set in the flags2 codec context field

‘k’

add extradata to all key packets

‘e’

add extradata to all packets

If not specified it is assumed ‘k’.

For example the following ffmpeg command forces a global
header (thus disabling individual packet headers) in the H.264 packets
generated by the libx264 encoder, but corrects them by adding
the header stored in extradata to the key packets:

Modifies the bitstream to fit in MOV and to be usable by the Final Cut
Pro decoder. This filter only applies to the mpeg2video codec, and is
likely not needed for Final Cut Pro 7 and newer with the appropriate
-tag:v.

Avery Lee, writing in the rec.video.desktop newsgroup in 2001,
commented that "MJPEG, or at least the MJPEG in AVIs having the
MJPG fourcc, is restricted JPEG with a fixed – and *omitted* –
Huffman table. The JPEG must be YCbCr colorspace, it must be 4:2:2,
and it must use basic Huffman encoding, not arithmetic or
progressive. . . . You can indeed extract the MJPEG frames and
decode them with a regular JPEG decoder, but you have to prepend
the DHT segment to them, or else the decoder won’t have any idea
how to decompress the data. The exact table necessary is given in
the OpenDML spec."

This bitstream filter patches the header of frames extracted from an MJPEG
stream (carrying the AVI1 header ID and lacking a DHT segment) to
produce fully qualified JPEG images.

DivX-style packed B-frames are not valid MPEG-4 and were only a
workaround for the broken Video for Windows subsystem.
They use more space, can cause minor AV sync issues, require more
CPU power to decode (unless the player has some decoded picture queue
to compensate the 2,0,2,0 frame per packet style) and cause
trouble if copied into a standard container like mp4 or mpeg-ps/ts,
because MPEG-4 decoders may not be able to decode them, since they are
not valid MPEG-4.

For example to fix an AVI file containing an MPEG-4 stream with
DivX-style packed B-frames using ffmpeg, you can use the command:

Damages the contents of packets without damaging the container. Can be
used for fuzzing or testing error resilience/concealment.

Parameters:
A numeral string, whose value is related to how often output bytes will
be modified. Therefore, values below or equal to 0 are forbidden, and
the lower the more frequent bytes will be modified, with 1 meaning
every byte is modified.

The libavformat library provides some generic global options, which
can be set on all the muxers and demuxers. In addition each muxer or
demuxer may support so-called private options, which are specific for
that component.

Options may be set by specifying -optionvalue in the
FFmpeg tools, or by setting the value explicitly in the
AVFormatContext options or using the libavutil/opt.h API
for programmatic use.

The list of supported options follows:

avioflags flags (input/output)

Possible values:

‘direct’

Reduce buffering.

probesize integer (input)

Set probing size in bytes, i.e. the size of the data to analyze to get
stream information. A higher value will enable detecting more
information in case it is dispersed into the stream, but will increase
latency. Must be an integer not lesser than 32. It is 5000000 by default.

packetsize integer (output)

Set packet size.

fflags flags (input/output)

Set format flags.

Possible values:

‘ignidx’

Ignore index.

‘fastseek’

Enable fast, but inaccurate seeks for some formats.

‘genpts’

Generate PTS.

‘nofillin’

Do not fill in missing values that can be exactly calculated.

‘noparse’

Disable AVParsers, this needs +nofillin too.

‘igndts’

Ignore DTS.

‘discardcorrupt’

Discard corrupted frames.

‘sortdts’

Try to interleave output packets by DTS.

‘keepside’

Do not merge side data.

‘latm’

Enable RTP MP4A-LATM payload.

‘nobuffer’

Reduce the latency introduced by optional buffering

‘bitexact’

Only write platform-, build- and time-independent data.
This ensures that file and data checksums are reproducible and match between
platforms. Its primary use is for regression testing.

‘shortest’

Stop muxing at the end of the shortest stream.
It may be needed to increase max_interleave_delta to avoid flushing the longer
streams before EOF.

seek2any integer (input)

Allow seeking to non-keyframes on demuxer level when supported if set to 1.
Default is 0.

analyzeduration integer (input)

Specify how many microseconds are analyzed to probe the input. A
higher value will enable detecting more accurate information, but will
increase latency. It defaults to 5,000,000 microseconds = 5 seconds.

cryptokey hexadecimal string (input)

Set decryption key.

indexmem integer (input)

Set max memory used for timestamp index (per stream).

rtbufsize integer (input)

Set max memory used for buffering real-time frames.

fdebug flags (input/output)

Print specific debug info.

Possible values:

‘ts’

max_delay integer (input/output)

Set maximum muxing or demuxing delay in microseconds.

fpsprobesize integer (input)

Set number of frames used to probe fps.

audio_preload integer (output)

Set microseconds by which audio packets should be interleaved earlier.

chunk_duration integer (output)

Set microseconds for each chunk.

chunk_size integer (output)

Set size in bytes for each chunk.

err_detect, f_err_detect flags (input)

Set error detection flags. f_err_detect is deprecated and
should be used only via the ffmpeg tool.

Possible values:

‘crccheck’

Verify embedded CRCs.

‘bitstream’

Detect bitstream specification deviations.

‘buffer’

Detect improper bitstream length.

‘explode’

Abort decoding on minor error detection.

‘careful’

Consider things that violate the spec and have not been seen in the
wild as errors.

‘compliant’

Consider all spec non compliancies as errors.

‘aggressive’

Consider things that a sane encoder should not do as an error.

max_interleave_delta integer (output)

Set maximum buffering duration for interleaving. The duration is
expressed in microseconds, and defaults to 1000000 (1 second).

To ensure all the streams are interleaved correctly, libavformat will
wait until it has at least one packet for each stream before actually
writing any packets to the output file. When some streams are
"sparse" (i.e. there are large gaps between successive packets), this
can result in excessive buffering.

This field specifies the maximum difference between the timestamps of the
first and the last packet in the muxing queue, above which libavformat
will output a packet regardless of whether it has queued a packet for all
the streams.

If set to 0, libavformat will continue buffering packets until it has
a packet for each stream, regardless of the maximum timestamp
difference between the buffered packets.

use_wallclock_as_timestamps integer (input)

Use wallclock as timestamps if set to 1. Default is 0.

avoid_negative_ts integer (output)

Possible values:

‘make_non_negative’

Shift timestamps to make them non-negative.
Also note that this affects only leading negative timestamps, and not
non-monotonic negative timestamps.

‘make_zero’

Shift timestamps so that the first timestamp is 0.

‘auto (default)’

Enables shifting when required by the target format.

‘disabled’

Disables shifting of timestamp.

When shifting is enabled, all output timestamps are shifted by the
same amount. Audio, video, and subtitles desynching and relative
timestamp differences are preserved compared to how they would have
been without shifting.

skip_initial_bytes integer (input)

Set number of bytes to skip before reading header and frames if set to 1.
Default is 0.

correct_ts_overflow integer (input)

Correct single timestamp overflows if set to 1. Default is 1.

flush_packets integer (output)

Flush the underlying I/O stream after each packet. Default 1 enables it, and
has the effect of reducing the latency; 0 disables it and may slightly
increase performance in some cases.

Format stream specifiers allow selection of one or more streams that
match specific properties.

Possible forms of stream specifiers are:

stream_index

Matches the stream with this index.

stream_type[:stream_index]

stream_type is one of following: ’v’ for video, ’a’ for audio,
’s’ for subtitle, ’d’ for data, and ’t’ for attachments. If
stream_index is given, then it matches the stream number
stream_index of this type. Otherwise, it matches all streams of
this type.

p:program_id[:stream_index]

If stream_index is given, then it matches the stream with number
stream_index in the program with the id
program_id. Otherwise, it matches all streams in the program.

#stream_id

Matches the stream by a format-specific ID.

The exact semantics of stream specifiers is defined by the
avformat_match_stream_specifier() function declared in the
libavformat/avformat.h header.

Demuxers are configured elements in FFmpeg that can read the
multimedia streams from a particular type of file.

When you configure your FFmpeg build, all the supported demuxers
are enabled by default. You can list all available ones using the
configure option --list-demuxers.

You can disable all the demuxers using the configure option
--disable-demuxers, and selectively enable a single demuxer with
the option --enable-demuxer=DEMUXER, or disable it
with the option --disable-demuxer=DEMUXER.

The option -formats of the ff* tools will display the list of
enabled demuxers.

This demuxer presents all AVStreams from all variant streams.
The id field is set to the bitrate variant index number. By setting
the discard flags on AVStreams (by pressing ’a’ or ’v’ in ffplay),
the caller can decide which variant streams to actually receive.
The total bitrate of the variant that the stream belongs to is
available in a metadata key named "variant_bitrate".

This demuxer is used to demux APNG files.
All headers, but the PNG signature, up to (but not including) the first
fcTL chunk are transmitted as extradata.
Frames are then split as being all the chunks between two fcTL ones, or
between the last fcTL and IEND chunks.

-ignore_loop bool

Ignore the loop variable in the file if set.

-max_fps int

Maximum framerate in frames per second (0 for no limit).

-default_fps int

Default framerate in frames per second when none is specified in the file
(0 meaning as fast as possible).

This demuxer reads a list of files and other directives from a text file and
demuxes them one after the other, as if all their packets had been muxed
together.

The timestamps in the files are adjusted so that the first file starts at 0
and each next file starts where the previous one finishes. Note that it is
done globally and may cause gaps if all streams do not have exactly the same
length.

All files must have the same streams (same codecs, same time base, etc.).

The duration of each file is used to adjust the timestamps of the next file:
if the duration is incorrect (because it was computed using the bit-rate or
because the file is truncated, for example), it can cause artifacts. The
duration directive can be used to override the duration stored in
each file.

The script is a text file in extended-ASCII, with one directive per line.
Empty lines, leading spaces and lines starting with ’#’ are ignored. The
following directive is recognized:

file path

Path to a file to read; special characters and spaces must be escaped with
backslash or single quotes.

All subsequent file-related directives apply to that file.

ffconcat version 1.0

Identify the script type and version. It also sets the safe option
to 1 if it was -1.

To make FFmpeg recognize the format automatically, this directive must
appear exactly as is (no extra space or byte-order-mark) on the very first
line of the script.

duration dur

Duration of the file. This information can be specified from the file;
specifying it here may be more efficient or help if the information from the
file is not available or accurate.

If the duration is set for all files, then it is possible to seek in the
whole concatenated video.

inpoint timestamp

In point of the file. When the demuxer opens the file it instantly seeks to the
specified timestamp. Seeking is done so that all streams can be presented
successfully at In point.

This directive works best with intra frame codecs, because for non-intra frame
ones you will usually get extra packets before the actual In point and the
decoded content will most likely contain frames before In point too.

For each file, packets before the file In point will have timestamps less than
the calculated start timestamp of the file (negative in case of the first
file), and the duration of the files (if not specified by the duration
directive) will be reduced based on their specified In point.

Because of potential packets before the specified In point, packet timestamps
may overlap between two concatenated files.

outpoint timestamp

Out point of the file. When the demuxer reaches the specified decoding
timestamp in any of the streams, it handles it as an end of file condition and
skips the current and all the remaining packets from all streams.

Out point is exclusive, which means that the demuxer will not output packets
with a decoding timestamp greater or equal to Out point.

This directive works best with intra frame codecs and formats where all streams
are tightly interleaved. For non-intra frame codecs you will usually get
additional packets with presentation timestamp after Out point therefore the
decoded content will most likely contain frames after Out point too. If your
streams are not tightly interleaved you may not get all the packets from all
streams before Out point and you may only will be able to decode the earliest
stream until Out point.

The duration of the files (if not specified by the duration
directive) will be reduced based on their specified Out point.

file_packet_metadata key=value

Metadata of the packets of the file. The specified metadata will be set for
each file packet. You can specify this directive multiple times to add multiple
metadata entries.

stream

Introduce a stream in the virtual file.
All subsequent stream-related directives apply to the last introduced
stream.
Some streams properties must be set in order to allow identifying the
matching streams in the subfiles.
If no streams are defined in the script, the streams from the first file are
copied.

exact_stream_id id

Set the id of the stream.
If this directive is given, the string with the corresponding id in the
subfiles will be used.
This is especially useful for MPEG-PS (VOB) files, where the order of the
streams is not reliable.

If set to 1, reject unsafe file paths. A file path is considered safe if it
does not contain a protocol specification and is relative and all components
only contain characters from the portable character set (letters, digits,
period, underscore and hyphen) and have no period at the beginning of a
component.

If set to 0, any file name is accepted.

The default is 1.

-1 is equivalent to 1 if the format was automatically
probed and 0 otherwise.

auto_convert

If set to 1, try to perform automatic conversions on packet data to make the
streams concatenable.
The default is 1.

Currently, the only conversion is adding the h264_mp4toannexb bitstream
filter to H.264 streams in MP4 format. This is necessary in particular if
there are resolution changes.

segment_time_metadata

If set to 1, every packet will contain the lavf.concat.start_time and the
lavf.concat.duration packet metadata values which are the start_time and
the duration of the respective file segments in the concatenated output
expressed in microseconds. The duration metadata is only set if it is known
based on the concat file.
The default is 0.

Set the minimum valid delay between frames in hundredths of seconds.
Range is 0 to 6000. Default value is 2.

max_gif_delay

Set the maximum valid delay between frames in hundredth of seconds.
Range is 0 to 65535. Default value is 65535 (nearly eleven minutes),
the maximum value allowed by the specification.

default_delay

Set the default delay between frames in hundredths of seconds.
Range is 0 to 6000. Default value is 10.

ignore_loop

GIF files can contain information to loop a certain number of times (or
infinitely). If ignore_loop is set to 1, then the loop setting
from the input will be ignored and looping will not occur. If set to 0,
then looping will occur and will cycle the number of times according to
the GIF. Default value is 1.

For example, with the overlay filter, place an infinitely looping GIF
over another video:

Note that in the above example the shortest option for overlay filter is
used to end the output video at the length of the shortest input file,
which in this case is input.mp4 as the GIF in this example loops
infinitely.

This demuxer reads from a list of image files specified by a pattern.
The syntax and meaning of the pattern is specified by the
option pattern_type.

The pattern may contain a suffix which is used to automatically
determine the format of the images contained in the files.

The size, the pixel format, and the format of each image must be the
same for all the files in the sequence.

This demuxer accepts the following options:

framerate

Set the frame rate for the video stream. It defaults to 25.

loop

If set to 1, loop over the input. Default value is 0.

pattern_type

Select the pattern type used to interpret the provided filename.

pattern_type accepts one of the following values.

none

Disable pattern matching, therefore the video will only contain the specified
image. You should use this option if you do not want to create sequences from
multiple images and your filenames may contain special pattern characters.

sequence

Select a sequence pattern type, used to specify a sequence of files
indexed by sequential numbers.

A sequence pattern may contain the string "%d" or "%0Nd", which
specifies the position of the characters representing a sequential
number in each filename matched by the pattern. If the form
"%d0Nd" is used, the string representing the number in each
filename is 0-padded and N is the total number of 0-padded
digits representing the number. The literal character ’%’ can be
specified in the pattern with the string "%%".

If the sequence pattern contains "%d" or "%0Nd", the first filename of
the file list specified by the pattern must contain a number
inclusively contained between start_number and
start_number+start_number_range-1, and all the following
numbers must be sequential.

For example the pattern "img-%03d.bmp" will match a sequence of
filenames of the form img-001.bmp, img-002.bmp, ...,
img-010.bmp, etc.; the pattern "i%%m%%g-%d.jpg" will match a
sequence of filenames of the form i%m%g-1.jpg,
i%m%g-2.jpg, ..., i%m%g-10.jpg, etc.

Note that the pattern must not necessarily contain "%d" or
"%0Nd", for example to convert a single image file
img.jpeg you can employ the command:

ffmpeg -i img.jpeg img.png

glob

Select a glob wildcard pattern type.

The pattern is interpreted like a glob() pattern. This is only
selectable if libavformat was compiled with globbing support.

glob_sequence (deprecated, will be removed)

Select a mixed glob wildcard/sequence pattern.

If your version of libavformat was compiled with globbing support, and
the provided pattern contains at least one glob meta character among
%*?[]{} that is preceded by an unescaped "%", the pattern is
interpreted like a glob() pattern, otherwise it is interpreted
like a sequence pattern.

All glob special characters %*?[]{} must be prefixed
with "%". To escape a literal "%" you shall use "%%".

For example the pattern foo-%*.jpeg will match all the
filenames prefixed by "foo-" and terminating with ".jpeg", and
foo-%?%?%?.jpeg will match all the filenames prefixed with
"foo-", followed by a sequence of three characters, and terminating
with ".jpeg".

This pattern type is deprecated in favor of glob and
sequence.

Default value is glob_sequence.

pixel_format

Set the pixel format of the images to read. If not specified the pixel
format is guessed from the first image file in the sequence.

start_number

Set the index of the file matched by the image file pattern to start
to read from. Default value is 0.

start_number_range

Set the index interval range to check when looking for the first image
file in the sequence, starting from start_number. Default value
is 5.

ts_from_file

If set to 1, will set frame timestamp to modification time of image file. Note
that monotonity of timestamps is not provided: images go in the same order as
without this option. Default value is 0.
If set to 2, will set frame timestamp to the modification time of the image file in
nanosecond precision.

video_size

Set the video size of the images to read. If not specified the video
size is guessed from the first image file in the sequence.

Some files have multiple tracks. The demuxer will pick the first track by
default. The track_index option can be used to select a different
track. Track indexes start at 0. The demuxer exports the number of tracks as
tracks meta data entry.

Set size limit for looking up a new synchronization. Default value is
65536.

fix_teletext_pts

Override teletext packet PTS and DTS values with the timestamps calculated
from the PCR of the first program which the teletext stream is part of and is
not discarded. Default value is 1, set this option to 0 if you want your
teletext packet PTS and DTS values untouched.

ts_packetsize

Output option carrying the raw packet size in bytes.
Show the detected raw packet size, cannot be set by the user.

scan_all_pmts

Scan and combine all PMTs. The value is an integer with value from -1
to 1 (-1 means automatic setting, 1 means enabled, 0 means
disabled). Default value is -1.

This demuxer allows reading of MJPEG, where each frame is represented as a part of
multipart/x-mixed-replace stream.

strict_mime_boundary

Default implementation applies a relaxed standard to multi-part MIME boundary detection,
to prevent regression with numerous existing endpoints not generating a proper MIME
MJPEG stream. Turning this option on by setting it to 1 will result in a stricter check
of the boundary value.

A SBG script can mix absolute and relative timestamps. If the script uses
either only absolute timestamps (including the script start time) or only
relative ones, then its layout is fixed, and the conversion is
straightforward. On the other hand, if the script mixes both kind of
timestamps, then the NOW reference for relative timestamps will be
taken from the current time of day at the time the script is read, and the
script layout will be frozen according to that reference. That means that if
the script is directly played, the actual times will match the absolute
timestamps up to the sound controller’s clock accuracy, but if the user
somehow pauses the playback or seeks, all times will be shifted accordingly.

FFmpeg is able to dump metadata from media files into a simple UTF-8-encoded
INI-like text file and then load it back using the metadata muxer/demuxer.

The file format is as follows:

A file consists of a header and a number of metadata tags divided into sections,
each on its own line.

The header is a ‘;FFMETADATA’ string, followed by a version number (now 1).

Metadata tags are of the form ‘key=value’

Immediately after header follows global metadata

After global metadata there may be sections with per-stream/per-chapter
metadata.

A section starts with the section name in uppercase (i.e. STREAM or CHAPTER) in
brackets (‘[’, ‘]’) and ends with next section or end of file.

At the beginning of a chapter section there may be an optional timebase to be
used for start/end values. It must be in form
‘TIMEBASE=num/den’, where num and den are
integers. If the timebase is missing then start/end times are assumed to
be in milliseconds.

Next a chapter section must contain chapter start and end times in form
‘START=num’, ‘END=num’, where num is a positive
integer.

Empty lines and lines starting with ‘;’ or ‘#’ are ignored.

Metadata keys or values containing special characters (‘=’, ‘;’,
‘#’, ‘\’ and a newline) must be escaped with a backslash ‘\’.

Note that whitespace in metadata (e.g. ‘foo = bar’) is considered to be
a part of the tag (in the example above key is ‘foo ’, value is
‘ bar’).

The libavformat library provides some generic global options, which
can be set on all the protocols. In addition each protocol may support
so-called private options, which are specific for that component.

The list of supported options follows:

protocol_whitelist list (input)

Set a ","-separated list of allowed protocols. "ALL" matches all protocols. Protocols
prefixed by "-" are disabled.
All protocols are allowed by default but protocols used by an another
protocol (nested protocols) are restricted to a per protocol subset.

Protocols are configured elements in FFmpeg that enable access to
resources that require specific protocols.

When you configure your FFmpeg build, all the supported protocols are
enabled by default. You can list all available ones using the
configure option "–list-protocols".

You can disable all the protocols using the configure option
"–disable-protocols", and selectively enable a protocol using the
option "–enable-protocol=PROTOCOL", or you can disable a
particular protocol using the option
"–disable-protocol=PROTOCOL".

The option "-protocols" of the ff* tools will display the list of
supported protocols.

All protocols accept the following options:

rw_timeout

Maximum time to wait for (network) read/write operations to complete,
in microseconds.

An URL that does not have a protocol prefix will be assumed to be a
file URL. Depending on the build, an URL that looks like a Windows
path with the drive letter at the beginning will also be assumed to be
a file URL (usually not the case in builds for unix-like systems).

For example to read from a file input.mpeg with ffmpeg
use the command:

ffmpeg -i file:input.mpeg output.mpeg

This protocol accepts the following options:

truncate

Truncate existing files on write, if set to 1. A value of 0 prevents
truncating. Default value is 1.

blocksize

Set I/O operation maximum block size, in bytes. Default value is
INT_MAX, which results in not limiting the requested block size.
Setting this value reasonably low improves user termination request reaction
time, which is valuable for files on slow medium.

Set timeout in microseconds of socket I/O operations used by the underlying low level
operation. By default it is set to -1, which means that the timeout is
not specified.

ftp-anonymous-password

Password used when login as anonymous user. Typically an e-mail address
should be used.

ftp-write-seekable

Control seekability of connection during encoding. If set to 1 the
resource is supposed to be seekable, if set to 0 it is assumed not
to be seekable. Default value is 0.

NOTE: Protocol can be used as output, but it is recommended to not do
it, unless special care is taken (tests, customized server configuration
etc.). Different FTP servers behave in different way during seek
operation. ff* tools may produce incomplete content due to server limitations.

This protocol accepts the following options:

follow

If set to 1, the protocol will retry reading at the end of the file, allowing
reading files that still are being written. In order for this to terminate,
you either need to use the rw_timeout option, or use the interrupt callback
(for API users).

Read Apple HTTP Live Streaming compliant segmented stream as
a uniform one. The M3U8 playlists describing the segments can be
remote HTTP resources or local files, accessed using the standard
file protocol.
The nested protocol is declared by specifying
"+proto" after the hls URI scheme name, where proto
is either "file" or "http".

Using this protocol is discouraged - the hls demuxer should work
just as well (if not, please report the issues) and is more complete.
To use the hls demuxer instead, simply use the direct URLs to the
m3u8 files.

Control seekability of connection. If set to 1 the resource is
supposed to be seekable, if set to 0 it is assumed not to be seekable,
if set to -1 it will try to autodetect if it is seekable. Default
value is -1.

chunked_post

If set to 1 use chunked Transfer-Encoding for posts, default is 1.

content_type

Set a specific content type for the POST messages or for listen mode.

http_proxy

set HTTP proxy to tunnel through e.g. http://example.com:1234

headers

Set custom HTTP headers, can override built in default headers. The
value must be a string encoding the headers.

multiple_requests

Use persistent connections if set to 1, default is 0.

post_data

Set custom HTTP post data.

user_agent

Override the User-Agent header. If not specified the protocol will use a
string describing the libavformat build. ("Lavf/<version>")

user-agent

This is a deprecated option, you can use user_agent instead it.

timeout

Set timeout in microseconds of socket I/O operations used by the underlying low level
operation. By default it is set to -1, which means that the timeout is
not specified.

reconnect_at_eof

If set then eof is treated like an error and causes reconnection, this is useful
for live / endless streams.

reconnect_streamed

If set then even streamed/non seekable streams will be reconnected on errors.

reconnect_delay_max

Sets the maximum delay in seconds after which to give up reconnecting

mime_type

Export the MIME type.

icy

If set to 1 request ICY (SHOUTcast) metadata from the server. If the server
supports this, the metadata has to be retrieved by the application by reading
the icy_metadata_headers and icy_metadata_packet options.
The default is 1.

If the server supports ICY metadata, and icy was set to 1, this
contains the last non-empty metadata packet sent by the server. It should be
polled in regular intervals by applications interested in mid-stream metadata
updates.

cookies

Set the cookies to be sent in future requests. The format of each cookie is the
same as the value of a Set-Cookie HTTP response field. Multiple cookies can be
delimited by a newline character.

offset

Set initial byte offset.

end_offset

Try to limit the request to bytes preceding this offset.

method

When used as a client option it sets the HTTP method for the request.

When used as a server option it sets the HTTP method that is going to be
expected from the client(s).
If the expected and the received HTTP method do not match the client will
be given a Bad Request response.
When unset the HTTP method is not checked for now. This will be replaced by
autodetection in the future.

listen

If set to 1 enables experimental HTTP server. This can be used to send data when
used as an output option, or read data from a client with HTTP POST when used as
an input option.
If set to 2 enables experimental multi-client HTTP server. This is not yet implemented
in ffmpeg.c or ffserver.c and thus must not be used as a command line option.

Some HTTP requests will be denied unless cookie values are passed in with the
request. The cookies option allows these cookies to be specified. At
the very least, each cookie must specify a value along with a path and domain.
HTTP requests that match both the domain and path will automatically include the
cookie value in the HTTP Cookie header field. Multiple cookies can be delimited
by a newline.

number is the number corresponding to the file descriptor of the
pipe (e.g. 0 for stdin, 1 for stdout, 2 for stderr). If number
is not specified, by default the stdout file descriptor will be used
for writing, stdin for reading.

Set I/O operation maximum block size, in bytes. Default value is
INT_MAX, which results in not limiting the requested block size.
Setting this value reasonably low improves user termination request reaction
time, which is valuable if data transmission is slow.

Note that some formats (typically MOV), require the output protocol to
be seekable, so they will fail with the pipe output protocol.

The Real-Time Messaging Protocol (RTMP) is used for streaming multimedia
content across a TCP/IP network.

The required syntax is:

rtmp://[username:password@]server[:port][/app][/instance][/playpath]

The accepted parameters are:

username

An optional username (mostly for publishing).

password

An optional password (mostly for publishing).

server

The address of the RTMP server.

port

The number of the TCP port to use (by default is 1935).

app

It is the name of the application to access. It usually corresponds to
the path where the application is installed on the RTMP server
(e.g. /ondemand/, /flash/live/, etc.). You can override
the value parsed from the URI through the rtmp_app option, too.

playpath

It is the path or name of the resource to play with reference to the
application specified in app, may be prefixed by "mp4:". You
can override the value parsed from the URI through the rtmp_playpath
option, too.

listen

Act as a server, listening for an incoming connection.

timeout

Maximum time to wait for the incoming connection. Implies listen.

Additionally, the following parameters can be set via command line options
(or in code via AVOptions):

rtmp_app

Name of application to connect on the RTMP server. This option
overrides the parameter specified in the URI.

rtmp_buffer

Set the client buffer time in milliseconds. The default is 3000.

rtmp_conn

Extra arbitrary AMF connection parameters, parsed from a string,
e.g. like B:1 S:authMe O:1 NN:code:1.23 NS:flag:ok O:0.
Each value is prefixed by a single character denoting the type,
B for Boolean, N for number, S for string, O for object, or Z for null,
followed by a colon. For Booleans the data must be either 0 or 1 for
FALSE or TRUE, respectively. Likewise for Objects the data must be 0 or
1 to end or begin an object, respectively. Data items in subobjects may
be named, by prefixing the type with ’N’ and specifying the name before
the value (i.e. NB:myFlag:1). This option may be used multiple
times to construct arbitrary AMF sequences.

rtmp_flashver

Version of the Flash plugin used to run the SWF player. The default
is LNX 9,0,124,2. (When publishing, the default is FMLE/3.0 (compatible;
<libavformat version>).)

rtmp_flush_interval

Number of packets flushed in the same request (RTMPT only). The default
is 10.

rtmp_live

Specify that the media is a live stream. No resuming or seeking in
live streams is possible. The default value is any, which means the
subscriber first tries to play the live stream specified in the
playpath. If a live stream of that name is not found, it plays the
recorded stream. The other possible values are live and
recorded.

rtmp_pageurl

URL of the web page in which the media was embedded. By default no
value will be sent.

rtmp_playpath

Stream identifier to play or to publish. This option overrides the
parameter specified in the URI.

rtmp_subscribe

Name of live stream to subscribe to. By default no value will be sent.
It is only sent if the option is specified or if rtmp_live
is set to live.

rtmp_swfhash

SHA256 hash of the decompressed SWF file (32 bytes).

rtmp_swfsize

Size of the decompressed SWF file, required for SWFVerification.

rtmp_swfurl

URL of the SWF player for the media. By default no value will be sent.

rtmp_swfverify

URL to player swf file, compute hash/size automatically.

rtmp_tcurl

URL of the target stream. Defaults to proto://host[:port]/app.

For example to read with ffplay a multimedia resource named
"sample" from the application "vod" from an RTMP server "myserver":

ffplay rtmp://myserver/vod/sample

To publish to a password protected server, passing the playpath and
app names separately:

Real-Time Messaging Protocol and its variants supported through
librtmp.

Requires the presence of the librtmp headers and library during
configuration. You need to explicitly configure the build with
"–enable-librtmp". If enabled this will replace the native RTMP
protocol.

This protocol provides most client functions and a few server
functions needed to support RTMP, RTMP tunneled in HTTP (RTMPT),
encrypted RTMP (RTMPE), RTMP over SSL/TLS (RTMPS) and tunneled
variants of these encrypted types (RTMPTE, RTMPTS).

The required syntax is:

rtmp_proto://server[:port][/app][/playpath] options

where rtmp_proto is one of the strings "rtmp", "rtmpt", "rtmpe",
"rtmps", "rtmpte", "rtmpts" corresponding to each RTMP variant, and
server, port, app and playpath have the same
meaning as specified for the RTMP native protocol.
options contains a list of space-separated options of the form
key=val.

See the librtmp manual page (man 3 librtmp) for more information.

For example, to stream a file in real-time to an RTMP server using
ffmpeg:

RTSP is not technically a protocol handler in libavformat, it is a demuxer
and muxer. The demuxer supports both normal RTSP (with data transferred
over RTP; this is used by e.g. Apple and Microsoft) and Real-RTSP (with
data transferred over RDT).

The muxer can be used to send a stream using RTSP ANNOUNCE to a server
supporting it (currently Darwin Streaming Server and Mischa Spiegelmock’s
RTSP server).

The required syntax for a RTSP url is:

rtsp://hostname[:port]/path

Options can be set on the ffmpeg/ffplay command
line, or set in code via AVOptions or in
avformat_open_input.

The following options are supported.

initial_pause

Do not start playing the stream immediately if set to 1. Default value
is 0.

rtsp_transport

Set RTSP transport protocols.

It accepts the following values:

‘udp’

Use UDP as lower transport protocol.

‘tcp’

Use TCP (interleaving within the RTSP control channel) as lower
transport protocol.

‘udp_multicast’

Use UDP multicast as lower transport protocol.

‘http’

Use HTTP tunneling as lower transport protocol, which is useful for
passing proxies.

Multiple lower transport protocols may be specified, in that case they are
tried one at a time (if the setup of one fails, the next one is tried).
For the muxer, only the ‘tcp’ and ‘udp’ options are supported.

rtsp_flags

Set RTSP flags.

The following values are accepted:

‘filter_src’

Accept packets only from negotiated peer address and port.

‘listen’

Act as a server, listening for an incoming connection.

‘prefer_tcp’

Try TCP for RTP transport first, if TCP is available as RTSP RTP transport.

Default value is ‘none’.

allowed_media_types

Set media types to accept from the server.

The following flags are accepted:

‘video’

‘audio’

‘data’

By default it accepts all media types.

min_port

Set minimum local UDP port. Default value is 5000.

max_port

Set maximum local UDP port. Default value is 65000.

timeout

Set maximum timeout (in seconds) to wait for incoming connections.

A value of -1 means infinite (default). This option implies the
rtsp_flags set to ‘listen’.

reorder_queue_size

Set number of packets to buffer for handling of reordered packets.

stimeout

Set socket TCP I/O timeout in microseconds.

user-agent

Override User-Agent header. If not specified, it defaults to the
libavformat identifier string.

When receiving data over UDP, the demuxer tries to reorder received packets
(since they may arrive out of order, or packets may get lost totally). This
can be disabled by setting the maximum demuxing delay to zero (via
the max_delay field of AVFormatContext).

When watching multi-bitrate Real-RTSP streams with ffplay, the
streams to display can be chosen with -vstn and
-astn for video and audio respectively, and can be switched
on the fly by pressing v and a.

Session Announcement Protocol (RFC 2974). This is not technically a
protocol handler in libavformat, it is a muxer and demuxer.
It is used for signalling of RTP streams, by announcing the SDP for the
streams regularly on a separate port.

The RTP packets are sent to destination on port port,
or to port 5004 if no port is specified.
options is a &-separated list. The following options
are supported:

announce_addr=address

Specify the destination IP address for sending the announcements to.
If omitted, the announcements are sent to the commonly used SAP
announcement multicast address 224.2.127.254 (sap.mcast.net), or
ff0e::2:7ffe if destination is an IPv6 address.

announce_port=port

Specify the port to send the announcements on, defaults to
9875 if not specified.

ttl=ttl

Specify the time to live value for the announcements and RTP packets,
defaults to 255.

same_port=0|1

If set to 1, send all RTP streams on the same port pair. If zero (the
default), all streams are sent on unique ports, with each stream on a
port 2 numbers higher than the previous.
VLC/Live555 requires this to be set to 1, to be able to receive the stream.
The RTP stack in libavformat for receiving requires all streams to be sent
on unique ports.

Set input and output encoding parameters, which are expressed by a
base64-encoded representation of a binary block. The first 16 bytes of
this binary block are used as master key, the following 14 bytes are
used as master salt.

The following parameters can be set via command line options
(or in code via AVOptions):

ca_file, cafile=filename

A file containing certificate authority (CA) root certificates to treat
as trusted. If the linked TLS library contains a default this might not
need to be specified for verification to work, but not all libraries and
setups have defaults built in.
The file must be in OpenSSL PEM format.

tls_verify=1|0

If enabled, try to verify the peer that we are communicating with.
Note, if using OpenSSL, this currently only makes sure that the
peer certificate is signed by one of the root certificates in the CA
database, but it does not validate that the certificate actually
matches the host name we are trying to connect to. (With GnuTLS,
the host name is validated as well.)

This is disabled by default since it requires a CA database to be
provided by the caller in many cases.

cert_file, cert=filename

A file containing a certificate to use in the handshake with the peer.
(When operating as server, in listen mode, this is more often required
by the peer, while client certificates only are mandated in certain
setups.)

key_file, key=filename

A file containing the private key for the certificate.

listen=1|0

If enabled, listen for connections on the provided port, and assume
the server role in the handshake instead of the client role.

In case threading is enabled on the system, a circular buffer is used
to store the incoming data, which allows one to reduce loss of data due to
UDP socket buffer overruns. The fifo_size and
overrun_nonfatal options are related to this buffer.

The list of supported options follows.

buffer_size=size

Set the UDP maximum socket buffer size in bytes. This is used to set either
the receive or send buffer size, depending on what the socket is used for.
Default is 64KB. See also fifo_size.

bitrate=bitrate

If set to nonzero, the output will have the specified constant bitrate if the
input has enough packets to sustain it.

burst_bits=bits

When using bitrate this specifies the maximum number of bits in
packet bursts.

localport=port

Override the local UDP port to bind with.

localaddr=addr

Choose the local IP address. This is useful e.g. if sending multicast
and the host has multiple interfaces, where the user can choose
which interface to send on by specifying the IP address of that interface.

pkt_size=size

Set the size in bytes of UDP packets.

reuse=1|0

Explicitly allow or disallow reusing UDP sockets.

ttl=ttl

Set the time to live value (for multicast only).

connect=1|0

Initialize the UDP socket with connect(). In this case, the
destination address can’t be changed with ff_udp_set_remote_url later.
If the destination address isn’t known at the start, this option can
be specified in ff_udp_set_remote_url, too.
This allows finding out the source address for the packets with getsockname,
and makes writes return with AVERROR(ECONNREFUSED) if "destination
unreachable" is received.
For receiving, this gives the benefit of only receiving packets from
the specified peer address/port.

sources=address[,address]

Only receive packets sent to the multicast group from one of the
specified sender IP addresses.

block=address[,address]

Ignore packets sent to the multicast group from the specified
sender IP addresses.

fifo_size=units

Set the UDP receiving circular buffer size, expressed as a number of
packets with size of 188 bytes. If not specified defaults to 7*4096.

The libavdevice library provides the same interface as
libavformat. Namely, an input device is considered like a demuxer, and
an output device like a muxer, and the interface and generic device
options are the same provided by libavformat (see the ffmpeg-formats
manual).

In addition each input or output device may support so-called private
options, which are specific for that component.

Options may be set by specifying -optionvalue in the
FFmpeg tools, or by setting the value explicitly in the device
AVFormatContext options or using the libavutil/opt.h API
for programmatic use.

Input devices are configured elements in FFmpeg which enable accessing
the data coming from a multimedia device attached to your system.

When you configure your FFmpeg build, all the supported input devices
are enabled by default. You can list all available ones using the
configure option "–list-indevs".

You can disable all the input devices using the configure option
"–disable-indevs", and selectively enable an input device using the
option "–enable-indev=INDEV", or you can disable a particular
input device using the option "–disable-indev=INDEV".

The option "-devices" of the ff* tools will display the list of
supported input devices.

AVFoundation is the currently recommended framework by Apple for streamgrabbing on OSX >= 10.7 as well as on iOS.
The older QTKit framework has been marked deprecated since OSX version 10.7.

The input filename has to be given in the following syntax:

-i "[[VIDEO]:[AUDIO]]"

The first entry selects the video input while the latter selects the audio input.
The stream has to be specified by the device name or the device index as shown by the device list.
Alternatively, the video and/or audio input device can be chosen by index using the
-video_device_index <INDEX>
and/or
-audio_device_index <INDEX>
, overriding any
device name or index given in the input filename.

All available devices can be enumerated by using -list_devices true, listing
all device names and corresponding indices.

There are two device name aliases:

default

Select the AVFoundation default device of the corresponding type.

none

Do not record the corresponding media type.
This is equivalent to specifying an empty device name or index.

If set to true, a list of all available input devices is given showing all
device names and indices.

-video_device_index <INDEX>

Specify the video device by its index. Overrides anything given in the input filename.

-audio_device_index <INDEX>

Specify the audio device by its index. Overrides anything given in the input filename.

-pixel_format <FORMAT>

Request the video device to use a specific pixel format.
If the specified format is not supported, a list of available formats is given
and the first one in this list is used instead. Available pixel formats are:
monob, rgb555be, rgb555le, rgb565be, rgb565le, rgb24, bgr24, 0rgb, bgr0, 0bgr, rgb0,
bgr48be, uyvy422, yuva444p, yuva444p16le, yuv444p, yuv422p16, yuv422p10, yuv444p10,
yuv420p, nv12, yuyv422, gray

-framerate

Set the grabbing frame rate. Default is ntsc, corresponding to a
frame rate of 30000/1001.

To enable this input device, you need the Blackmagic DeckLink SDK and you
need to configure with the appropriate --extra-cflags
and --extra-ldflags.
On Windows, you need to run the IDL files through widl.

DeckLink is very picky about the formats it supports. Pixel format is
uyvy422 or v210, framerate and video size must be determined for your device with
-list_formats 1. Audio sample rate is always 48 kHz and the number
of channels can be 2, 8 or 16. Note that all audio channels are bundled in one single
audio track.

If set to true, print a list of supported formats and exit.
Defaults to false.

bm_v210

If set to ‘1’, video is captured in 10 bit v210 instead
of uyvy422. Not all Blackmagic devices support this option.

teletext_lines

If set to nonzero, an additional teletext stream will be captured from the
vertical ancillary data. This option is a bitmask of the VBI lines checked,
specifically lines 6 to 22, and lines 318 to 335. Line 6 is the LSB in the mask.
Selected lines which do not contain teletext information will be ignored. You
can use the special all constant to select all possible lines, or
standard to skip lines 6, 318 and 319, which are not compatible with all
receivers. Capturing teletext only works for SD PAL sources in 8 bit mode.
To use this option, ffmpeg needs to be compiled with --enable-libzvbi.

channels

Defines number of audio channels to capture. Must be ‘2’, ‘8’ or ‘16’.
Defaults to ‘2’.

duplex_mode

Sets the decklink device duplex mode. Must be ‘unset’, ‘half’ or ‘full’.
Defaults to ‘unset’.

Select video input pin number for crossbar device. This will be
routed to the crossbar device’s Video Decoder output pin.
Note that changing this value can affect future invocations
(sets a new default) until system reboot occurs.

crossbar_audio_input_pin_number

Select audio input pin number for crossbar device. This will be
routed to the crossbar device’s Audio Decoder output pin.
Note that changing this value can affect future invocations
(sets a new default) until system reboot occurs.

show_video_device_dialog

If set to true, before capture starts, popup a display dialog
to the end user, allowing them to change video filter properties
and configurations manually.
Note that for crossbar devices, adjusting values in this dialog
may be needed at times to toggle between PAL (25 fps) and NTSC (29.97)
input frame rates, sizes, interlacing, etc. Changing these values can
enable different scan rates/frame rates and avoiding green bars at
the bottom, flickering scan lines, etc.
Note that with some devices, changing these properties can also affect future
invocations (sets new defaults) until system reboot occurs.

show_audio_device_dialog

If set to true, before capture starts, popup a display dialog
to the end user, allowing them to change audio filter properties
and configurations manually.

show_video_crossbar_connection_dialog

If set to true, before capture starts, popup a display
dialog to the end user, allowing them to manually
modify crossbar pin routings, when it opens a video device.

show_audio_crossbar_connection_dialog

If set to true, before capture starts, popup a display
dialog to the end user, allowing them to manually
modify crossbar pin routings, when it opens an audio device.

show_analog_tv_tuner_dialog

If set to true, before capture starts, popup a display
dialog to the end user, allowing them to manually
modify TV channels and frequencies.

show_analog_tv_tuner_audio_dialog

If set to true, before capture starts, popup a display
dialog to the end user, allowing them to manually
modify TV audio (like mono vs. stereo, Language A,B or C).

audio_device_load

Load an audio capture filter device from file instead of searching
it by name. It may load additional parameters too, if the filter
supports the serialization of its properties to.
To use this an audio capture source has to be specified, but it can
be anything even fake one.

audio_device_save

Save the currently used audio capture filter device and its
parameters (if the filter supports it) to a file.
If a file with the same name exists it will be overwritten.

video_device_load

Load a video capture filter device from file instead of searching
it by name. It may load additional parameters too, if the filter
supports the serialization of its properties to.
To use this a video capture source has to be specified, but it can
be anything even fake one.

video_device_save

Save the currently used video capture filter device and its
parameters (if the filter supports it) to a file.
If a file with the same name exists it will be overwritten.

Set the video frame size. The default is to capture the full screen if desktop is selected, or the full window size if title=window_title is selected.

offset_x

When capturing a region with video_size, set the distance from the left edge of the screen or desktop.

Note that the offset calculation is from the top left corner of the primary monitor on Windows. If you have a monitor positioned to the left of your primary monitor, you will need to use a negative offset_x value to move the region to that monitor.

offset_y

When capturing a region with video_size, set the distance from the top edge of the screen or desktop.

Note that the offset calculation is from the top left corner of the primary monitor on Windows. If you have a monitor positioned above your primary monitor, you will need to use a negative offset_y value to move the region to that monitor.

To enable this input device, you need libiec61883, libraw1394 and
libavc1394 installed on your system. Use the configure option
--enable-libiec61883 to compile with the device enabled.

The iec61883 capture device supports capturing from a video device
connected via IEEE1394 (FireWire), using libiec61883 and the new Linux
FireWire stack (juju). This is the default DV/HDV input method in Linux
Kernel 2.6.37 and later, since the old FireWire stack was removed.

Specify the FireWire port to be used as input file, or "auto"
to choose the first port connected.

Override autodetection of DV/HDV. This should only be used if auto
detection does not work, or if usage of a different device type
should be prohibited. Treating a DV device as HDV (or vice versa) will
not work and result in undefined behavior.
The values auto, dv and hdv are supported.

dvbuffer

Set maximum size of buffer for incoming data, in frames. For DV, this
is an exact value. For HDV, it is not frame exact, since HDV does
not have a fixed frame size.

dvguid

Select the capture device by specifying its GUID. Capturing will only
be performed from the specified device and fails if no device with the
given GUID is found. This is useful to select the input if multiple
devices are connected at the same time.
Look at /sys/bus/firewire/devices to find out the GUIDs.

To enable this input device during configuration you need libjack
installed on your system.

A JACK input device creates one or more JACK writable clients, one for
each audio channel, with name client_name:input_N, where
client_name is the name provided by the application, and N
is a number which identifies the channel.
Each writable client will send the acquired data to the FFmpeg input
device.

Once you have created one or more JACK readable clients, you need to
connect them to one or more JACK writable clients.

To connect or disconnect JACK clients you can use the jack_connect
and jack_disconnect programs, or do it through a graphical interface,
for example with qjackctl.

To list the JACK clients and their properties you can invoke the command
jack_lsp.

Follows an example which shows how to capture a JACK readable client
with ffmpeg.

This input device reads data from the open output pads of a libavfilter
filtergraph.

For each filtergraph open output, the input device will create a
corresponding stream which is mapped to the generated output. Currently
only video data is supported. The filtergraph is specified through the
option graph.

Specify the filtergraph to use as input. Each video open output must be
labelled by a unique string of the form "outN", where N is a
number starting from 0 corresponding to the mapped input stream
generated by the device.
The first unlabelled output is automatically assigned to the "out0"
label, but all the others need to be specified explicitly.

The suffix "+subcc" can be appended to the output label to create an extra
stream with the closed captions packets attached to that output
(experimental; only for EIA-608 / CEA-708 for now).
The subcc streams are created after all the normal streams, in the order of
the corresponding stream.
For example, if there is "out19+subcc", "out7+subcc" and up to "out42", the
stream #43 is subcc for stream #7 and stream #44 is subcc for stream #19.

If not specified defaults to the filename specified for the input
device.

graph_file

Set the filename of the filtergraph to be read and sent to the other
filters. Syntax of the filtergraph is the same as the one specified by
the option graph.

The speed is specified CD-ROM speed units. The speed is set through
the libcdio cdio_cddap_speed_set function. On many CD-ROM
drives, specifying a value too large will result in using the fastest
speed.

paranoia_mode

Set paranoia recovery mode flags. It accepts one of the following values:

‘disable’

‘verify’

‘overlap’

‘neverskip’

‘full’

Default value is ‘disable’.

For more information about the available recovery modes, consult the
paranoia project documentation.

The OpenAL input device provides audio capture on all systems with a
working OpenAL 1.1 implementation.

To enable this input device during configuration, you need OpenAL
headers and libraries installed on your system, and need to configure
FFmpeg with --enable-openal.

OpenAL headers and libraries should be provided as part of your OpenAL
implementation, or as an additional download (an SDK). Depending on your
installation you may need to specify additional flags via the
--extra-cflags and --extra-ldflags for allowing the build
system to locate the OpenAL headers and libraries.

An incomplete list of OpenAL implementations follows:

Creative

The official Windows implementation, providing hardware acceleration
with supported devices and software fallback.
See http://openal.org/.

OpenAL Soft

Portable, open source (LGPL) software implementation. Includes
backends for the most common sound APIs on the Windows, Linux,
Solaris, and BSD operating systems.
See http://kcat.strangesoft.net/openal.html.

This device allows one to capture from an audio input device handled
through OpenAL.

You need to specify the name of the device to capture in the provided
filename. If the empty string is provided, the device will
automatically select the default device. You can get the list of the
supported devices by using the option list_devices.

The filename passed as input is parsed to contain either a device name or index.
The device index can also be given by using -video_device_index.
A given device index will override any given device name.
If the desired device consists of numbers only, use -video_device_index to identify it.
The default device will be chosen if an empty string or the device name "default" is given.
The available devices can be enumerated by using -list_devices.

If FFmpeg is built with v4l-utils support (by using the
--enable-libv4l2 configure option), it is possible to use it with the
-use_libv4l2 input device option.

The name of the device to grab is a file device node, usually Linux
systems tend to automatically create such nodes when the device
(e.g. an USB webcam) is plugged into the system, and has a name of the
kind /dev/videoN, where N is a number associated to
the device.

Video4Linux2 devices usually support a limited set of
widthxheight sizes and frame rates. You can check which are
supported using -list_formats all for Video4Linux2 devices.
Some devices, like TV cards, support one or more standards. It is possible
to list all the supported standards using -list_standards all.

The time base for the timestamps is 1 microsecond. Depending on the kernel
version and configuration, the timestamps may be derived from the real time
clock (origin at the Unix Epoch) or the monotonic clock (origin usually at
boot time, unaffected by NTP or manual changes to the clock). The
-timestamps abs or -ts abs option can be used to force
conversion into the real time clock.

Some usage examples of the video4linux2 device with ffmpeg
and ffplay:

List supported formats for a video4linux2 device:

ffplay -f video4linux2 -list_formats all /dev/video0

Grab and show the input of a video4linux2 device:

ffplay -f video4linux2 -framerate 30 -video_size hd720 /dev/video0

Grab and record the input of a video4linux2 device, leave the
frame rate and size as previously set:

hostname:display_number.screen_number specifies the
X11 display name of the screen to grab from. hostname can be
omitted, and defaults to "localhost". The environment variable
DISPLAY contains the default display name.

x_offset and y_offset specify the offsets of the grabbed
area with respect to the top-left border of the X11 screen. They
default to 0.

Specify whether to draw the mouse pointer. A value of 0 specifies
not to draw the pointer. Default value is 1.

follow_mouse

Make the grabbed area follow the mouse. The argument can be
centered or a number of pixels PIXELS.

When it is specified with "centered", the grabbing region follows the mouse
pointer and keeps the pointer at the center of region; otherwise, the region
follows only when the mouse pointer reaches within PIXELS (greater than
zero) to the edge of region.

Use the MIT-SHM extension for shared memory. Default value is 1.
It may be necessary to disable it for remote displays (legacy x11grab
only).

grab_x

grab_y

Set the grabbing region coordinates. They are expressed as offset from
the top left corner of the X11 window and correspond to the
x_offset and y_offset parameters in the device name. The
default value for both options is 0.

Options may be set by specifying -optionvalue in the
FFmpeg tools, option=value for the aresample filter,
by setting the value explicitly in the
SwrContext options or using the libavutil/opt.h API for
programmatic use.

ich, in_channel_count

Set the number of input channels. Default value is 0. Setting this
value is not mandatory if the corresponding channel layout
in_channel_layout is set.

och, out_channel_count

Set the number of output channels. Default value is 0. Setting this
value is not mandatory if the corresponding channel layout
out_channel_layout is set.

uch, used_channel_count

Set the number of used input channels. Default value is 0. This option is
only used for special remapping.

isr, in_sample_rate

Set the input sample rate. Default value is 0.

osr, out_sample_rate

Set the output sample rate. Default value is 0.

isf, in_sample_fmt

Specify the input sample format. It is set by default to none.

osf, out_sample_fmt

Specify the output sample format. It is set by default to none.

tsf, internal_sample_fmt

Set the internal sample format. Default value is none.
This will automatically be chosen when it is not explicitly set.

For swr only, set resampling phase shift, default value is 10, and must be in
the interval [0,30].

linear_interp

Use linear interpolation if set to 1, default value is 0.

exact_rational

For swr only, when enabled, try to use exact phase_count based on input and
output sample rate. However, if it is larger than 1 << phase_shift,
the phase_count will be 1 << phase_shift as fallback. Default is disabled.

cutoff

Set cutoff frequency (swr: 6dB point; soxr: 0dB point) ratio; must be a float
value between 0 and 1. Default value is 0.97 with swr, and 0.91 with soxr
(which, with a sample-rate of 44100, preserves the entire audio band to 20kHz).

precision

For soxr only, the precision in bits to which the resampled signal will be
calculated. The default value of 20 (which, with suitable dithering, is
appropriate for a destination bit-depth of 16) gives SoX’s ’High Quality’; a
value of 28 gives SoX’s ’Very High Quality’.

For swr only, simple 1 parameter audio sync to timestamps using stretching,
squeezing, filling and trimming. Setting this to 1 will enable filling and
trimming, larger values represent the maximum amount in samples that the data
may be stretched or squeezed for each second.
Default value is 0, thus no compensation is applied to make the samples match
the audio timestamps.

first_pts

For swr only, assume the first pts should be this value. The time unit is 1 / sample rate.
This allows for padding/trimming at the start of stream. By default, no
assumption is made about the first frame’s expected pts, so no padding or
trimming is done. For example, this could be set to 0 to pad the beginning with
silence if an audio stream starts after the video stream or to trim any samples
with a negative pts due to encoder delay.

min_comp

For swr only, set the minimum difference between timestamps and audio data (in
seconds) to trigger stretching/squeezing/filling or trimming of the
data to make it match the timestamps. The default is that
stretching/squeezing/filling and trimming is disabled
(min_comp = FLT_MAX).

min_hard_comp

For swr only, set the minimum difference between timestamps and audio data (in
seconds) to trigger adding/dropping samples to make it match the
timestamps. This option effectively is a threshold to select between
hard (trim/fill) and soft (squeeze/stretch) compensation. Note that
all compensation is by default disabled through min_comp.
The default is 0.1.

comp_duration

For swr only, set duration (in seconds) over which data is stretched/squeezed
to make it match the timestamps. Must be a non-negative double float value,
default value is 1.0.

max_soft_comp

For swr only, set maximum factor by which data is stretched/squeezed to make it
match the timestamps. Must be a non-negative double float value, default value
is 0.

This filtergraph splits the input stream in two streams, then sends one
stream through the crop filter and the vflip filter, before merging it
back with the other stream by overlaying it on top. You can use the
following command to achieve this:

The result will be that the top half of the video is mirrored
onto the bottom half of the output video.

Filters in the same linear chain are separated by commas, and distinct
linear chains of filters are separated by semicolons. In our example,
crop,vflip are in one linear chain, split and
overlay are separately in another. The points where the linear
chains join are labelled by names enclosed in square brackets. In the
example, the split filter generates two outputs that are associated to
the labels [main] and [tmp].

The stream sent to the second output of split, labelled as
[tmp], is processed through the crop filter, which crops
away the lower half part of the video, and then vertically flipped. The
overlay filter takes in input the first unchanged output of the
split filter (which was labelled as [main]), and overlay on its
lower half the output generated by the crop,vflip filterchain.

Some filters take in input a list of parameters: they are specified
after the filter name and an equal sign, and are separated from each other
by a colon.

There exist so-called source filters that do not have an
audio/video input, and sink filters that will not have audio/video
output.

can be used to create and display an image representing the graph
described by the GRAPH_DESCRIPTION string. Note that this string must be
a complete self-contained graph, with its inputs and outputs explicitly defined.
For example if your command line is of the form:

ffmpeg -i infile -vf scale=640:360 outfile

your GRAPH_DESCRIPTION string will need to be of the form:

nullsrc,scale=640:360,nullsink

you may also need to set the nullsrc parameters and add a format
filter in order to simulate a specific input file.

A filtergraph is a directed graph of connected filters. It can contain
cycles, and there can be multiple links between a pair of
filters. Each link has one input pad on one side connecting it to one
filter from which it takes its input, and one output pad on the other
side connecting it to one filter accepting its output.

Each filter in a filtergraph is an instance of a filter class
registered in the application, which defines the features and the
number of input and output pads of the filter.

A filter with no input pads is called a "source", and a filter with no
output pads is called a "sink".

A filtergraph has a textual representation, which is recognized by the
-filter/-vf/-af and
-filter_complex options in ffmpeg and
-vf/-af in ffplay, and by the
avfilter_graph_parse_ptr() function defined in
libavfilter/avfilter.h.

A filterchain consists of a sequence of connected filters, each one
connected to the previous one in the sequence. A filterchain is
represented by a list of ","-separated filter descriptions.

A filtergraph consists of a sequence of filterchains. A sequence of
filterchains is represented by a list of ";"-separated filterchain
descriptions.

A filter is represented by a string of the form:
[in_link_1]...[in_link_N]filter_name=arguments[out_link_1]...[out_link_M]

filter_name is the name of the filter class of which the
described filter is an instance of, and has to be the name of one of
the filter classes registered in the program.
The name of the filter class is optionally followed by a string
"=arguments".

arguments is a string which contains the parameters used to
initialize the filter instance. It may have one of two forms:

A ’:’-separated list of key=value pairs.

A ’:’-separated list of value. In this case, the keys are assumed to be
the option names in the order they are declared. E.g. the fade filter
declares three options in this order – type, start_frame and
nb_frames. Then the parameter list in:0:30 means that the value
in is assigned to the option type, 0 to
start_frame and 30 to nb_frames.

A ’:’-separated list of mixed direct value and long key=value
pairs. The direct value must precede the key=value pairs, and
follow the same constraints order of the previous point. The following
key=value pairs can be set in any preferred order.

If the option value itself is a list of items (e.g. the format filter
takes a list of pixel formats), the items in the list are usually separated by
‘|’.

The list of arguments can be quoted using the character ‘'’ as initial
and ending mark, and the character ‘\’ for escaping the characters
within the quoted text; otherwise the argument string is considered
terminated when the next special character (belonging to the set
‘[]=;,’) is encountered.

The name and arguments of the filter are optionally preceded and
followed by a list of link labels.
A link label allows one to name a link and associate it to a filter output
or input pad. The preceding labels in_link_1
... in_link_N, are associated to the filter input pads,
the following labels out_link_1 ... out_link_M, are
associated to the output pads.

When two link labels with the same name are found in the
filtergraph, a link between the corresponding input and output pad is
created.

If an output pad is not labelled, it is linked by default to the first
unlabelled input pad of the next filter in the filterchain.
For example in the filterchain

nullsrc, split[L1], [L2]overlay, nullsink

the split filter instance has two output pads, and the overlay filter
instance two input pads. The first output pad of split is labelled
"L1", the first input pad of overlay is labelled "L2", and the second
output pad of split is linked to the second input pad of overlay,
which are both unlabelled.

In a filter description, if the input label of the first filter is not
specified, "in" is assumed; if the output label of the last filter is not
specified, "out" is assumed.

In a complete filterchain all the unlabelled filter input and output
pads must be connected. A filtergraph is considered valid if all the
filter input and output pads of all the filterchains are connected.

Libavfilter will automatically insert scale filters where format
conversion is required. It is possible to specify swscale flags
for those automatically inserted scalers by prepending
sws_flags=flags;
to the filtergraph description.

A first level escaping affects the content of each filter option
value, which may contain the special character : used to
separate values, or one of the escaping characters \'.

A second level escaping affects the whole filter description, which
may contain the escaping characters \' or the special
characters [],; used by the filtergraph description.

Finally, when you specify a filtergraph on a shell commandline, you
need to perform a third level escaping for the shell special
characters contained within it.

For example, consider the following string to be embedded in
the drawtext filter description text value:

this is a 'string': may contain one, or more, special characters

This string contains the ' special escaping character, and the
: special character, so it needs to be escaped in this way:

text=this is a \'string\'\: may contain one, or more, special characters

A second level of escaping is required when embedding the filter
description in a filtergraph description, in order to escape all the
filtergraph special characters. Thus the example above becomes:

drawtext=text=this is a \\\'string\\\'\\: may contain one\, or more\, special characters

(note that in addition to the \' escaping special characters,
also , needs to be escaped).

Finally an additional level of escaping is needed when writing the
filtergraph description in a shell command, which depends on the
escaping rules of the adopted shell. For example, assuming that
\ is special and needs to be escaped with another \, the
previous string will finally result in:

-vf "drawtext=text=this is a \\\\\\'string\\\\\\'\\\\: may contain one\\, or more\\, special characters"

Some filters support a generic enable option. For the filters
supporting timeline editing, this option can be set to an expression which is
evaluated before sending a frame to the filter. If the evaluation is non-zero,
the filter will be enabled, otherwise the frame will be sent unchanged to the
next filter in the filtergraph.

The expression accepts the following values:

‘t’

timestamp expressed in seconds, NAN if the input timestamp is unknown

‘n’

sequential number of the input frame, starting from 0

‘pos’

the position in the file of the input frame, NAN if unknown

‘w’

‘h’

width and height of the input frame if video

Additionally, these filters support an enable command that can be used
to re-define the expression.

Like any other filtering option, the enable option follows the same
rules.

For example, to enable a blur filter (smartblur) from 10 seconds to 3
minutes, and a curves filter starting at 3 seconds:

A compressor is mainly used to reduce the dynamic range of a signal.
Especially modern music is mostly compressed at a high ratio to
improve the overall loudness. It’s done to get the highest attention
of a listener, "fatten" the sound and bring more "power" to the track.
If a signal is compressed too much it may sound dull or "dead"
afterwards or it may start to "pump" (which could be a powerful effect
but can also destroy a track completely).
The right compression is the key to reach a professional sound and is
the high art of mixing and mastering. Because of its complex settings
it may take a long time to get the right feeling for this kind of effect.

Compression is done by detecting the volume above a chosen level
threshold and dividing it by the factor set with ratio.
So if you set the threshold to -12dB and your signal reaches -6dB a ratio
of 2:1 will result in a signal at -9dB. Because an exact manipulation of
the signal would cause distortion of the waveform the reduction can be
levelled over the time. This is done by setting "Attack" and "Release".
attack determines how long the signal has to rise above the threshold
before any reduction will occur and release sets the time the signal
has to fall below the threshold to reduce the reduction again. Shorter signals
than the chosen attack time will be left untouched.
The overall reduction of the signal can be made up afterwards with the
makeup setting. So compressing the peaks of a signal about 6dB and
raising the makeup to this level results in a signal twice as loud than the
source. To gain a softer entry in the compression the knee flattens the
hard edge at the threshold in the range of the chosen decibels.

The filter accepts the following options:

level_in

Set input gain. Default is 1. Range is between 0.015625 and 64.

threshold

If a signal of second stream rises above this level it will affect the gain
reduction of the first stream.
By default it is 0.125. Range is between 0.00097563 and 1.

ratio

Set a ratio by which the signal is reduced. 1:2 means that if the level
rose 4dB above the threshold, it will be only 2dB above after the reduction.
Default is 2. Range is between 1 and 20.

attack

Amount of milliseconds the signal has to rise above the threshold before gain
reduction starts. Default is 20. Range is between 0.01 and 2000.

release

Amount of milliseconds the signal has to fall below the threshold before
reduction is decreased again. Default is 250. Range is between 0.01 and 9000.

makeup

Set the amount by how much signal will be amplified after processing.
Default is 2. Range is from 1 and 64.

knee

Curve the sharp knee around the threshold to enter gain reduction more softly.
Default is 2.82843. Range is between 1 and 8.

link

Choose if the average level between all channels of input stream
or the louder(maximum) channel of input stream affects the
reduction. Default is average.

detection

Should the exact signal be taken in case of peak or an RMS one in case
of rms. Default is rms which is mostly smoother.

mix

How much to use compressed signal in output. Default is 1.
Range is between 0 and 1.

This filter is bit crusher with enhanced functionality. A bit crusher
is used to audibly reduce number of bits an audio signal is sampled
with. This doesn’t change the bit depth at all, it just produces the
effect. Material reduced in bit depth sounds more harsh and "digital".
This filter is able to even round to continuous values instead of discrete
bit depths.
Additionally it has a D/C offset which results in different crushing of
the lower and the upper half of the signal.
An Anti-Aliasing setting is able to produce "softer" crushing sounds.

Another feature of this filter is the logarithmic mode.
This setting switches from linear distances between bits to logarithmic ones.
The result is a much more "natural" sounding crusher which doesn’t gate low
signals for example. The human ear has a logarithmic perception, too
so this kind of crushing is much more pleasant.
Logarithmic crushing is also able to get anti-aliased.

Set list of delays in milliseconds for each channel separated by ’|’.
At least one delay greater than 0 should be provided.
Unused delays will be silently ignored. If number of given delays is
smaller than number of channels all remaining channels will not be delayed.
If you want to delay exact number of samples, append ’S’ to number.

Echoes are reflected sound and can occur naturally amongst mountains
(and sometimes large buildings) when talking or shouting; digital echo
effects emulate this behaviour and are often used to help fill out the
sound of a single instrument or vocal. The time difference between the
original signal and the reflection is the delay, and the
loudness of the reflected signal is the decay.
Multiple echoes can have different delays and decays.

A description of the accepted parameters follows.

in_gain

Set input gain of reflected signal. Default is 0.6.

out_gain

Set output gain of reflected signal. Default is 0.3.

delays

Set list of time intervals in milliseconds between original signal and reflections
separated by ’|’. Allowed range for each delay is (0 - 90000.0].
Default is 1000.

decays

Set list of loudnesses of reflected signals separated by ’|’.
Allowed range for each decay is (0 - 1.0].
Default is 0.5.

Audio emphasis filter creates or restores material directly taken from LPs or
emphased CDs with different filter curves. E.g. to store music on vinyl the
signal has to be altered by a filter first to even out the disadvantages of
this recording medium.
Once the material is played back the inverse filter has to be applied to
restore the distortion of the frequency response.

The filter accepts the following options:

level_in

Set input gain.

level_out

Set output gain.

mode

Set filter mode. For restoring material use reproduction mode, otherwise
use production mode. Default is reproduction mode.

This filter accepts one or more expressions (one for each channel),
which are evaluated and used to modify a corresponding audio signal.

It accepts the following parameters:

exprs

Set the ’|’-separated expressions list for each separate channel. If
the number of input channels is greater than the number of
expressions, the last specified expression is used for the remaining
output channels.

channel_layout, c

Set output channel layout. If not specified, the channel layout is
specified by the number of expressions. If set to ‘same’, it will
use by default the same input channel layout.

Each expression in exprs can contain the following constants and functions:

ch

channel number of the current expression

n

number of the evaluated sample, starting from 0

s

sample rate

t

time of the evaluated sample expressed in seconds

nb_in_channels

nb_out_channels

input and output number of channels

val(CH)

the value of input channel with number CH

Note: this filter is slow. For faster processing you should use a
dedicated filter.

Specify the effect type, can be either in for fade-in, or
out for a fade-out effect. Default is in.

start_sample, ss

Specify the number of the start sample for starting to apply the fade
effect. Default is 0.

nb_samples, ns

Specify the number of samples for which the fade effect has to last. At
the end of the fade-in effect the output audio will have the same
volume as the input audio, at the end of the fade-out transition
the output audio will be silence. Default is 44100.

Specify the duration of the fade effect. See
(ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual
for the accepted syntax.
At the end of the fade-in effect the output audio will have the same
volume as the input audio, at the end of the fade-out transition
the output audio will be silence.
By default the duration is determined by nb_samples.
If set this option is used instead of nb_samples.

Set frequency domain real expression for each separate channel separated
by ’|’. Default is "1".
If the number of input channels is greater than the number of
expressions, the last specified expression is used for the remaining
output channels.

imag

Set frequency domain imaginary expression for each separate channel
separated by ’|’. If not set, real option is used.

Each expression in real and imag can contain the following
constants:

sr

sample rate

b

current frequency bin number

nb

number of available bins

ch

channel number of the current expression

chs

number of channels

pts

current frame pts

win_size

Set window size.

It accepts the following values:

‘w16’

‘w32’

‘w64’

‘w128’

‘w256’

‘w512’

‘w1024’

‘w2048’

‘w4096’

‘w8192’

‘w16384’

‘w32768’

‘w65536’

Default is w4096

win_func

Set window function. Default is hann.

overlap

Set window overlap. If set to 1, the recommended overlap for selected
window function will be picked. Default is 0.75.

A gate is mainly used to reduce lower parts of a signal. This kind of signal
processing reduces disturbing noise between useful signals.

Gating is done by detecting the volume below a chosen level threshold
and dividing it by the factor set with ratio. The bottom of the noise
floor is set via range. Because an exact manipulation of the signal
would cause distortion of the waveform the reduction can be levelled over
time. This is done by setting attack and release.

attack determines how long the signal has to fall below the threshold
before any reduction will occur and release sets the time the signal
has to rise above the threshold to reduce the reduction again.
Shorter signals than the chosen attack time will be left untouched.

level_in

Set input level before filtering.
Default is 1. Allowed range is from 0.015625 to 64.

range

Set the level of gain reduction when the signal is below the threshold.
Default is 0.06125. Allowed range is from 0 to 1.

threshold

If a signal rises above this level the gain reduction is released.
Default is 0.125. Allowed range is from 0 to 1.

ratio

Set a ratio by which the signal is reduced.
Default is 2. Allowed range is from 1 to 9000.

attack

Amount of milliseconds the signal has to rise above the threshold before gain
reduction stops.
Default is 20 milliseconds. Allowed range is from 0.01 to 9000.

release

Amount of milliseconds the signal has to fall below the threshold before the
reduction is increased again. Default is 250 milliseconds.
Allowed range is from 0.01 to 9000.

makeup

Set amount of amplification of signal after processing.
Default is 1. Allowed range is from 1 to 64.

knee

Curve the sharp knee around the threshold to enter gain reduction more softly.
Default is 2.828427125. Allowed range is from 1 to 8.

detection

Choose if exact signal should be taken for detection or an RMS like one.
Default is rms. Can be peak or rms.

link

Choose if the average level between all channels or the louder channel affects
the reduction.
Default is average. Can be average or maximum.

The limiter prevents an input signal from rising over a desired threshold.
This limiter uses lookahead technology to prevent your signal from distorting.
It means that there is a small delay after the signal is processed. Keep in mind
that the delay it produces is the attack time you set.

The filter accepts the following options:

level_in

Set input gain. Default is 1.

level_out

Set output gain. Default is 1.

limit

Don’t let signals above this level pass the limiter. Default is 1.

attack

The limiter will reach its attenuation level in this amount of time in
milliseconds. Default is 5 milliseconds.

release

Come back from limiting to attenuation 1.0 in this amount of milliseconds.
Default is 50 milliseconds.

asc

When gain reduction is always needed ASC takes care of releasing to an
average reduction level rather than reaching a reduction of 0 in the release
time.

asc_level

Select how much the release time is affected by ASC, 0 means nearly no changes
in release time while 1 produces higher release times.

level

Auto level output signal. Default is enabled.
This normalizes audio back to 0dB if enabled.

Depending on picked setting it is recommended to upsample input 2x or 4x times
with aresample before applying this filter.

If the channel layouts of the inputs are disjoint, and therefore compatible,
the channel layout of the output will be set accordingly and the channels
will be reordered as necessary. If the channel layouts of the inputs are not
disjoint, the output will have all the channels of the first input then all
the channels of the second input, in that order, and the channel layout of
the output will be the default value corresponding to the total number of
channels.

For example, if the first input is in 2.1 (FL+FR+LF) and the second input
is FC+BL+BR, then the output will be in 5.1, with the channels in the
following order: a1, a2, b1, a3, b2, b3 (a1 is the first channel of the
first input, b1 is the first channel of the second input).

On the other hand, if both input are in stereo, the output channels will be
in the default order: a1, a2, b1, b2, and the channel layout will be
arbitrarily set to 4.0, which may or may not be the expected value.

All inputs must have the same sample rate, and format.

If inputs do not have the same duration, the output will stop with the
shortest.

Note that this filter only supports float samples (the amerge
and pan audio filters support many formats). If the amix
input has integer samples then aresample will be automatically
inserted to perform the conversion to float samples.

This option string is in format:
"cchn f=cf w=w g=g t=f | ..."
Each equalizer band is separated by ’|’.

chn

Set channel number to which equalization will be applied.
If input doesn’t have that channel the entry is ignored.

f

Set central frequency for band.
If input doesn’t have that frequency the entry is ignored.

w

Set band width in hertz.

g

Set band gain in dB.

t

Set filter type for band, optional, can be:

‘0’

Butterworth, this is default.

‘1’

Chebyshev type 1.

‘2’

Chebyshev type 2.

curves

With this option activated frequency response of anequalizer is displayed
in video stream.

size

Set video stream size. Only useful if curves option is activated.

mgain

Set max gain that will be displayed. Only useful if curves option is activated.
Setting this to a reasonable value makes it possible to display gain which is derived from
neighbour bands which are too close to each other and thus produce higher gain
when both are activated.

fscale

Set frequency scale used to draw frequency response in video output.
Can be linear or logarithmic. Default is logarithmic.

colors

Set color for each channel curve which is going to be displayed in video stream.
This is list of color names separated by space or by ’|’.
Unrecognised or missing colors will be replaced by white color.

fN is existing filter number, starting from 0, if no such filter is available
error is returned.
freq set new frequency parameter.
width set new width parameter in herz.
gain set new gain parameter in dB.

Full filter invocation with asendcmd may look like this:
asendcmd=c=’4.0 anequalizer change 0|f=200|w=50|g=1’,anequalizer=...

This can be used together with ffmpeg-shortest to
extend audio streams to the same length as the video stream.

A description of the accepted options follows.

packet_size

Set silence packet size. Default value is 4096.

pad_len

Set the number of samples of silence to add to the end. After the
value is reached, the stream is terminated. This option is mutually
exclusive with whole_len.

whole_len

Set the minimum total number of samples in the output audio stream. If
the value is longer than the input audio length, silence is added to
the end, until the value is reached. This option is mutually exclusive
with pad_len.

If neither the pad_len nor the whole_len option is
set, the filter will add silence to the end of the input stream
indefinitely.

Audio pulsator is something between an autopanner and a tremolo.
But it can produce funny stereo effects as well. Pulsator changes the volume
of the left and right channel based on a LFO (low frequency oscillator) with
different waveforms and shifted phases.
This filter have the ability to define an offset between left and right
channel. An offset of 0 means that both LFO shapes match each other.
The left and right channel are altered equally - a conventional tremolo.
An offset of 50% means that the shape of the right channel is exactly shifted
in phase (or moved backwards about half of the frequency) - pulsator acts as
an autopanner. At 1 both curves match again. Every setting in between moves the
phase shift gapless between all stages and produces some "bypassing" sounds with
sine and triangle waveforms. The more you set the offset near 1 (starting from
the 0.5) the faster the signal passes from the left to the right speaker.

The filter accepts the following options:

level_in

Set input gain. By default it is 1. Range is [0.015625 - 64].

level_out

Set output gain. By default it is 1. Range is [0.015625 - 64].

mode

Set waveform shape the LFO will use. Can be one of: sine, triangle, square,
sawup or sawdown. Default is sine.

amount

Set modulation. Define how much of original signal is affected by the LFO.

offset_l

Set left channel offset. Default is 0. Allowed range is [0 - 1].

offset_r

Set right channel offset. Default is 0.5. Allowed range is [0 - 1].

width

Set pulse width. Default is 1. Allowed range is [0 - 2].

timing

Set possible timing mode. Can be one of: bpm, ms or hz. Default is hz.

bpm

Set bpm. Default is 120. Allowed range is [30 - 300]. Only used if timing
is set to bpm.

ms

Set ms. Default is 500. Allowed range is [10 - 2000]. Only used if timing
is set to ms.

hz

Set frequency in Hz. Default is 2. Allowed range is [0.01 - 100]. Only used
if timing is set to hz.

Resample the input audio to the specified parameters, using the
libswresample library. If none are specified then the filter will
automatically convert between its input and output.

This filter is also able to stretch/squeeze the audio data to make it match
the timestamps or to inject silence / cut out audio to make it match the
timestamps, do a combination of both or do neither.

The filter accepts the syntax
[sample_rate:]resampler_options, where sample_rate
expresses a sample rate and resampler_options is a list of
key=value pairs, separated by ":". See the
ffmpeg-resampler manual for the complete list of supported options.

This filter is not built by default, please use aresample to do squeezing/stretching.

It accepts the following parameters:

compensate

Enable stretching/squeezing the data to make it match the timestamps. Disabled
by default. When disabled, time gaps are covered with silence.

min_delta

The minimum difference between timestamps and audio data (in seconds) to trigger
adding/dropping samples. The default value is 0.1. If you get an imperfect
sync with this filter, try setting this parameter to 0.

max_comp

The maximum compensation in samples per second. Only relevant with compensate=1.
The default value is 500.

first_pts

Assume that the first PTS should be this value. The time base is 1 / sample
rate. This allows for padding/trimming at the start of the stream. By default,
no assumption is made about the first frame’s expected PTS, so no padding or
trimming is done. For example, this could be set to 0 to pad the beginning with
silence if an audio stream starts after the video stream or to trim any samples
with a negative PTS due to encoder delay.

Note that the first two sets of the start/end options and the duration
option look at the frame timestamp, while the _sample options simply count the
samples that pass through the filter. So start/end_pts and start/end_sample will
give different results when the timestamps are wrong, inexact or do not start at
zero. Also note that this filter does not modify the timestamps. If you wish
to have the output timestamps start at zero, insert the asetpts filter after the
atrim filter.

If multiple start or end options are set, this filter tries to be greedy and
keep all samples that match at least one of the specified constraints. To keep
only the part that matches all the constraints at once, chain multiple atrim
filters.

The defaults are such that all the input is kept. So it is possible to set e.g.
just the end values to keep everything before the specified time.

Boost or cut the bass (lower) frequencies of the audio using a two-pole
shelving filter with a response similar to that of a standard
hi-fi’s tone-controls. This is also known as shelving equalisation (EQ).

The filter accepts the following options:

gain, g

Give the gain at 0 Hz. Its useful range is about -20
(for a large cut) to +20 (for a large boost).
Beware of clipping when using a positive gain.

frequency, f

Set the filter’s central frequency and so can be used
to extend or reduce the frequency range to be boosted or cut.
The default value is 100 Hz.

Map channels from input to output. The argument is a ’|’-separated list of
mappings, each in the in_channel-out_channel or
in_channel form. in_channel can be either the name of the input
channel (e.g. FL for front left) or its index in the input channel layout.
out_channel is the name of the output channel or its index in the output
channel layout. If out_channel is not given then it is implicitly an
index, starting with zero and increasing by one for each mapping.

If no mapping is present, the filter will implicitly map input channels to
output channels, preserving indices.

For example, assuming a 5.1+downmix input MOV file,

ffmpeg -i in.mov -filter 'channelmap=map=DL-FL|DR-FR' out.wav

will create an output WAV file tagged as stereo from the downmix channels of
the input.

Can make a single vocal sound like a chorus, but can also be applied to instrumentation.

Chorus resembles an echo effect with a short delay, but whereas with echo the delay is
constant, with chorus, it is varied using using sinusoidal or triangular modulation.
The modulation depth defines the range the modulated delay is played before or after
the delay. Hence the delayed sound will sound slower or faster, that is the delayed
sound tuned around the original one, like in a chorus where some vocals are slightly
off key.

A list of times in seconds for each channel over which the instantaneous level
of the input signal is averaged to determine its volume. attacks refers to
increase of volume and decays refers to decrease of volume. For most
situations, the attack time (response to the audio getting louder) should be
shorter than the decay time, because the human ear is more sensitive to sudden
loud audio than sudden soft audio. A typical value for attack is 0.3 seconds and
a typical value for decay is 0.8 seconds.
If specified number of attacks & decays is lower than number of channels, the last
set attack/decay will be used for all remaining channels.

points

A list of points for the transfer function, specified in dB relative to the
maximum possible signal amplitude. Each key points list must be defined using
the following syntax: x0/y0|x1/y1|x2/y2|.... or
x0/y0 x1/y1 x2/y2 ....

The input values must be in strictly increasing order but the transfer function
does not have to be monotonically rising. The point 0/0 is assumed but
may be overridden (by 0/out-dBn). Typical values for the transfer
function are -70/-70|-60/-20.

soft-knee

Set the curve radius in dB for all joints. It defaults to 0.01.

gain

Set the additional gain in dB to be applied at all points on the transfer
function. This allows for easy adjustment of the overall gain.
It defaults to 0.

volume

Set an initial volume, in dB, to be assumed for each channel when filtering
starts. This permits the user to supply a nominal level initially, so that, for
example, a very large gain is not applied to initial signal levels before the
companding has begun to operate. A typical value for audio which is initially
quiet is -90 dB. It defaults to 0.

delay

Set a delay, in seconds. The input audio is analyzed immediately, but audio is
delayed before being fed to the volume adjuster. Specifying a delay
approximately equal to the attack/decay times allows the filter to effectively
operate in predictive rather than reactive mode. It defaults to 0.

Compensation Delay Line is a metric based delay to compensate differing
positions of microphones or speakers.

For example, you have recorded guitar with two microphones placed in
different location. Because the front of sound wave has fixed speed in
normal conditions, the phasing of microphones can vary and depends on
their location and interposition. The best sound mix can be achieved when
these microphones are in phase (synchronized). Note that distance of
~30 cm between microphones makes one microphone to capture signal in
antiphase to another microphone. That makes the final mix sounding moody.
This filter helps to solve phasing problems by adding different delays
to each microphone track and make them synchronized.

The best result can be reached when you take one track as base and
synchronize other tracks one by one with it.
Remember that synchronization/delay tolerance depends on sample rate, too.
Higher sample rates will give more tolerance.

It accepts the following parameters:

mm

Set millimeters distance. This is compensation distance for fine tuning.
Default is 0.

cm

Set cm distance. This is compensation distance for tightening distance setup.
Default is 0.

m

Set meters distance. This is compensation distance for hard distance setup.
Default is 0.

dry

Set dry amount. Amount of unprocessed (dry) signal.
Default is 0.

wet

Set wet amount. Amount of processed (wet) signal.
Default is 1.

temp

Set temperature degree in Celsius. This is the temperature of the environment.
Default is 20.

This can be useful to remove a DC offset (caused perhaps by a hardware problem
in the recording chain) from the audio. The effect of a DC offset is reduced
headroom and hence volume. The astats filter can be used to determine if
a signal has a DC offset.

shift

Set the DC shift, allowed range is [-1, 1]. It indicates the amount to shift
the audio.

limitergain

Optional. It should have a value much less than 1 (e.g. 0.05 or 0.02) and is
used to prevent clipping.

This filter applies a certain amount of gain to the input audio in order
to bring its peak magnitude to a target level (e.g. 0 dBFS). However, in
contrast to more "simple" normalization algorithms, the Dynamic Audio
Normalizer *dynamically* re-adjusts the gain factor to the input audio.
This allows for applying extra gain to the "quiet" sections of the audio
while avoiding distortions or clipping the "loud" sections. In other words:
The Dynamic Audio Normalizer will "even out" the volume of quiet and loud
sections, in the sense that the volume of each section is brought to the
same target level. Note, however, that the Dynamic Audio Normalizer achieves
this goal *without* applying "dynamic range compressing". It will retain 100%
of the dynamic range *within* each section of the audio file.

f

Set the frame length in milliseconds. In range from 10 to 8000 milliseconds.
Default is 500 milliseconds.
The Dynamic Audio Normalizer processes the input audio in small chunks,
referred to as frames. This is required, because a peak magnitude has no
meaning for just a single sample value. Instead, we need to determine the
peak magnitude for a contiguous sequence of sample values. While a "standard"
normalizer would simply use the peak magnitude of the complete file, the
Dynamic Audio Normalizer determines the peak magnitude individually for each
frame. The length of a frame is specified in milliseconds. By default, the
Dynamic Audio Normalizer uses a frame length of 500 milliseconds, which has
been found to give good results with most files.
Note that the exact frame length, in number of samples, will be determined
automatically, based on the sampling rate of the individual input audio file.

g

Set the Gaussian filter window size. In range from 3 to 301, must be odd
number. Default is 31.
Probably the most important parameter of the Dynamic Audio Normalizer is the
window size of the Gaussian smoothing filter. The filter’s window size
is specified in frames, centered around the current frame. For the sake of
simplicity, this must be an odd number. Consequently, the default value of 31
takes into account the current frame, as well as the 15 preceding frames and
the 15 subsequent frames. Using a larger window results in a stronger
smoothing effect and thus in less gain variation, i.e. slower gain
adaptation. Conversely, using a smaller window results in a weaker smoothing
effect and thus in more gain variation, i.e. faster gain adaptation.
In other words, the more you increase this value, the more the Dynamic Audio
Normalizer will behave like a "traditional" normalization filter. On the
contrary, the more you decrease this value, the more the Dynamic Audio
Normalizer will behave like a dynamic range compressor.

p

Set the target peak value. This specifies the highest permissible magnitude
level for the normalized audio input. This filter will try to approach the
target peak magnitude as closely as possible, but at the same time it also
makes sure that the normalized signal will never exceed the peak magnitude.
A frame’s maximum local gain factor is imposed directly by the target peak
magnitude. The default value is 0.95 and thus leaves a headroom of 5%*.
It is not recommended to go above this value.

m

Set the maximum gain factor. In range from 1.0 to 100.0. Default is 10.0.
The Dynamic Audio Normalizer determines the maximum possible (local) gain
factor for each input frame, i.e. the maximum gain factor that does not
result in clipping or distortion. The maximum gain factor is determined by
the frame’s highest magnitude sample. However, the Dynamic Audio Normalizer
additionally bounds the frame’s maximum gain factor by a predetermined
(global) maximum gain factor. This is done in order to avoid excessive gain
factors in "silent" or almost silent frames. By default, the maximum gain
factor is 10.0, For most inputs the default value should be sufficient and
it usually is not recommended to increase this value. Though, for input
with an extremely low overall volume level, it may be necessary to allow even
higher gain factors. Note, however, that the Dynamic Audio Normalizer does
not simply apply a "hard" threshold (i.e. cut off values above the threshold).
Instead, a "sigmoid" threshold function will be applied. This way, the
gain factors will smoothly approach the threshold value, but never exceed that
value.

r

Set the target RMS. In range from 0.0 to 1.0. Default is 0.0 - disabled.
By default, the Dynamic Audio Normalizer performs "peak" normalization.
This means that the maximum local gain factor for each frame is defined
(only) by the frame’s highest magnitude sample. This way, the samples can
be amplified as much as possible without exceeding the maximum signal
level, i.e. without clipping. Optionally, however, the Dynamic Audio
Normalizer can also take into account the frame’s root mean square,
abbreviated RMS. In electrical engineering, the RMS is commonly used to
determine the power of a time-varying signal. It is therefore considered
that the RMS is a better approximation of the "perceived loudness" than
just looking at the signal’s peak magnitude. Consequently, by adjusting all
frames to a constant RMS value, a uniform "perceived loudness" can be
established. If a target RMS value has been specified, a frame’s local gain
factor is defined as the factor that would result in exactly that RMS value.
Note, however, that the maximum local gain factor is still restricted by the
frame’s highest magnitude sample, in order to prevent clipping.

n

Enable channels coupling. By default is enabled.
By default, the Dynamic Audio Normalizer will amplify all channels by the same
amount. This means the same gain factor will be applied to all channels, i.e.
the maximum possible gain factor is determined by the "loudest" channel.
However, in some recordings, it may happen that the volume of the different
channels is uneven, e.g. one channel may be "quieter" than the other one(s).
In this case, this option can be used to disable the channel coupling. This way,
the gain factor will be determined independently for each channel, depending
only on the individual channel’s highest magnitude sample. This allows for
harmonizing the volume of the different channels.

c

Enable DC bias correction. By default is disabled.
An audio signal (in the time domain) is a sequence of sample values.
In the Dynamic Audio Normalizer these sample values are represented in the
-1.0 to 1.0 range, regardless of the original input format. Normally, the
audio signal, or "waveform", should be centered around the zero point.
That means if we calculate the mean value of all samples in a file, or in a
single frame, then the result should be 0.0 or at least very close to that
value. If, however, there is a significant deviation of the mean value from
0.0, in either positive or negative direction, this is referred to as a
DC bias or DC offset. Since a DC bias is clearly undesirable, the Dynamic
Audio Normalizer provides optional DC bias correction.
With DC bias correction enabled, the Dynamic Audio Normalizer will determine
the mean value, or "DC correction" offset, of each input frame and subtract
that value from all of the frame’s sample values which ensures those samples
are centered around 0.0 again. Also, in order to avoid "gaps" at the frame
boundaries, the DC correction offset values will be interpolated smoothly
between neighbouring frames.

b

Enable alternative boundary mode. By default is disabled.
The Dynamic Audio Normalizer takes into account a certain neighbourhood
around each frame. This includes the preceding frames as well as the
subsequent frames. However, for the "boundary" frames, located at the very
beginning and at the very end of the audio file, not all neighbouring
frames are available. In particular, for the first few frames in the audio
file, the preceding frames are not known. And, similarly, for the last few
frames in the audio file, the subsequent frames are not known. Thus, the
question arises which gain factors should be assumed for the missing frames
in the "boundary" region. The Dynamic Audio Normalizer implements two modes
to deal with this situation. The default boundary mode assumes a gain factor
of exactly 1.0 for the missing frames, resulting in a smooth "fade in" and
"fade out" at the beginning and at the end of the input, respectively.

s

Set the compress factor. In range from 0.0 to 30.0. Default is 0.0.
By default, the Dynamic Audio Normalizer does not apply "traditional"
compression. This means that signal peaks will not be pruned and thus the
full dynamic range will be retained within each local neighbourhood. However,
in some cases it may be desirable to combine the Dynamic Audio Normalizer’s
normalization algorithm with a more "traditional" compression.
For this purpose, the Dynamic Audio Normalizer provides an optional compression
(thresholding) function. If (and only if) the compression feature is enabled,
all input frames will be processed by a soft knee thresholding function prior
to the actual normalization process. Put simply, the thresholding function is
going to prune all samples whose magnitude exceeds a certain threshold value.
However, the Dynamic Audio Normalizer does not simply apply a fixed threshold
value. Instead, the threshold value will be adjusted for each individual
frame.
In general, smaller parameters result in stronger compression, and vice versa.
Values below 3.0 are not recommended, because audible distortion may appear.

This filter adds ‘cues’ to 44.1kHz stereo (i.e. audio CD format) audio
so that when listened to on headphones the stereo image is moved from
inside your head (standard for headphones) to outside and in front of
the listener (standard for speakers).

Apply a two-pole peaking equalisation (EQ) filter. With this
filter, the signal-level at and around a selected frequency can
be increased or decreased, whilst (unlike bandpass and bandreject
filters) that at all other frequencies is unchanged.

In order to produce complex equalisation curves, this filter can
be given several times, each with a different central frequency.

The filter accepts the following options:

frequency, f

Set the filter’s central frequency in Hz.

width_type

Set method to specify band-width of filter.

h

Hz

q

Q-Factor

o

octave

s

slope

width, w

Specify the band-width of a filter in width_type units.

gain, g

Set the required gain or attenuation in dB.
Beware of clipping when using a positive gain.

The filter supports the Peak Extend and Low-level Gain Adjustment features
of HDCD, and detects the Transient Filter flag.

ffmpeg -i HDCD16.flac -af hdcd OUT24.flac

When using the filter with wav, note the default encoding for wav is 16-bit,
so the resulting 20-bit stream will be truncated back to 16-bit. Use something
like -acodec pcm_s24le after the filter to get 24-bit PCM output.

Disable any automatic format conversion or resampling in the filter graph.

process_stereo

Process the stereo channels together. If target_gain does not match between
channels, consider it invalid and use the last valid target_gain.

cdt_ms

Set the code detect timer period in ms.

force_pe

Always extend peaks above -3dBFS even if PE isn’t signaled.

analyze_mode

Replace audio with a solid tone and adjust the amplitude to signal some
specific aspect of the decoding process. The output file can be loaded in
an audio editor alongside the original to aid analysis.

analyze_mode=pe:force_pe=true can be used to see all samples above the PE level.

Map channels from inputs to output. The argument is a ’|’-separated list of
mappings, each in the input_idx.in_channel-out_channel
form. input_idx is the 0-based index of the input stream. in_channel
can be either the name of the input channel (e.g. FL for front left) or its
index in the specified input stream. out_channel is the name of the output
channel.

The filter will attempt to guess the mappings when they are not specified
explicitly. It does so by first trying to find an unused matching input channel
and if that fails it picks the first unused input channel.

To enable compilation of this filter you need to configure FFmpeg with
--enable-ladspa.

file, f

Specifies the name of LADSPA plugin library to load. If the environment
variable LADSPA_PATH is defined, the LADSPA plugin is searched in
each one of the directories specified by the colon separated list in
LADSPA_PATH, otherwise in the standard LADSPA paths, which are in
this order: HOME/.ladspa/lib/, /usr/local/lib/ladspa/,
/usr/lib/ladspa/.

plugin, p

Specifies the plugin within the library. Some libraries contain only
one plugin, but others contain many of them. If this is not set filter
will list all available plugins within the specified library.

controls, c

Set the ’|’ separated list of controls which are zero or more floating point
values that determine the behavior of the loaded plugin (for example delay,
threshold or gain).
Controls need to be defined using the following syntax:
c0=value0|c1=value1|c2=value2|..., where
valuei is the value set on the i-th control.
Alternatively they can be also defined using the following syntax:
value0|value1|value2|..., where
valuei is the value set on the i-th control.
If controls is set to help, all available controls and
their valid ranges are printed.

sample_rate, s

Specify the sample rate, default to 44100. Only used if plugin have
zero inputs.

nb_samples, n

Set the number of samples per channel per each output frame, default
is 1024. Only used if plugin have zero inputs.

duration, d

Set the minimum duration of the sourced audio. See
(ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual
for the accepted syntax.
Note that the resulting duration may be greater than the specified duration,
as the generated audio is always cut at the end of a complete frame.
If not specified, or the expressed duration is negative, the audio is
supposed to be generated forever.
Only used if plugin have zero inputs.

EBU R128 loudness normalization. Includes both dynamic and linear normalization modes.
Support for both single pass (livestreams, files) and double pass (files) modes.
This algorithm can target IL, LRA, and maximum true peak.

Set offset gain. Gain is applied before the true-peak limiter.
Range is -99.0 - +99.0. Default is +0.0.

linear

Normalize linearly if possible.
measured_I, measured_LRA, measured_TP, and measured_thresh must also
to be specified in order to use this mode.
Options are true or false. Default is true.

dual_mono

Treat mono input files as "dual-mono". If a mono file is intended for playback
on a stereo system, its EBU R128 measurement will be perceptually incorrect.
If set to true, this option will compensate for this effect.
Multi-channel input files are not affected by this option.
Options are true or false. Default is false.

print_format

Set print format for stats. Options are summary, json, or none.
Default value is none.

This filter acts like normal compressor but has the ability to compress
detected signal using second input signal.
It needs two input streams and returns one output stream.
First input stream will be processed depending on second stream signal.
The filtered signal then can be filtered with other filters in later stages of
processing. See pan and amerge filter.

The filter accepts the following options:

level_in

Set input gain. Default is 1. Range is between 0.015625 and 64.

threshold

If a signal of second stream raises above this level it will affect the gain
reduction of first stream.
By default is 0.125. Range is between 0.00097563 and 1.

ratio

Set a ratio about which the signal is reduced. 1:2 means that if the level
raised 4dB above the threshold, it will be only 2dB above after the reduction.
Default is 2. Range is between 1 and 20.

attack

Amount of milliseconds the signal has to rise above the threshold before gain
reduction starts. Default is 20. Range is between 0.01 and 2000.

release

Amount of milliseconds the signal has to fall below the threshold before
reduction is decreased again. Default is 250. Range is between 0.01 and 9000.

makeup

Set the amount by how much signal will be amplified after processing.
Default is 2. Range is from 1 and 64.

knee

Curve the sharp knee around the threshold to enter gain reduction more softly.
Default is 2.82843. Range is between 1 and 8.

link

Choose if the average level between all channels of side-chain stream
or the louder(maximum) channel of side-chain stream affects the
reduction. Default is average.

detection

Should the exact signal be taken in case of peak or an RMS one in case
of rms. Default is rms which is mainly smoother.

level_sc

Set sidechain gain. Default is 1. Range is between 0.015625 and 64.

mix

How much to use compressed signal in output. Default is 1.
Range is between 0 and 1.

A sidechain gate acts like a normal (wideband) gate but has the ability to
filter the detected signal before sending it to the gain reduction stage.
Normally a gate uses the full range signal to detect a level above the
threshold.
For example: If you cut all lower frequencies from your sidechain signal
the gate will decrease the volume of your track only if not enough highs
appear. With this technique you are able to reduce the resonation of a
natural drum or remove "rumbling" of muted strokes from a heavily distorted
guitar.
It needs two input streams and returns one output stream.
First input stream will be processed depending on second stream signal.

The filter accepts the following options:

level_in

Set input level before filtering.
Default is 1. Allowed range is from 0.015625 to 64.

range

Set the level of gain reduction when the signal is below the threshold.
Default is 0.06125. Allowed range is from 0 to 1.

threshold

If a signal rises above this level the gain reduction is released.
Default is 0.125. Allowed range is from 0 to 1.

ratio

Set a ratio about which the signal is reduced.
Default is 2. Allowed range is from 1 to 9000.

attack

Amount of milliseconds the signal has to rise above the threshold before gain
reduction stops.
Default is 20 milliseconds. Allowed range is from 0.01 to 9000.

release

Amount of milliseconds the signal has to fall below the threshold before the
reduction is increased again. Default is 250 milliseconds.
Allowed range is from 0.01 to 9000.

makeup

Set amount of amplification of signal after processing.
Default is 1. Allowed range is from 1 to 64.

knee

Curve the sharp knee around the threshold to enter gain reduction more softly.
Default is 2.828427125. Allowed range is from 1 to 8.

detection

Choose if exact signal should be taken for detection or an RMS like one.
Default is rms. Can be peak or rms.

link

Choose if the average level between all channels or the louder channel affects
the reduction.
Default is average. Can be average or maximum.

This value is used to indicate if audio should be trimmed at beginning of
the audio. A value of zero indicates no silence should be trimmed from the
beginning. When specifying a non-zero value, it trims audio up until it
finds non-silence. Normally, when trimming silence from beginning of audio
the start_periods will be 1 but it can be increased to higher
values to trim all audio up to specific count of non-silence periods.
Default value is 0.

start_duration

Specify the amount of time that non-silence must be detected before it stops
trimming audio. By increasing the duration, bursts of noises can be treated
as silence and trimmed off. Default value is 0.

start_threshold

This indicates what sample value should be treated as silence. For digital
audio, a value of 0 may be fine but for audio recorded from analog,
you may wish to increase the value to account for background noise.
Can be specified in dB (in case "dB" is appended to the specified value)
or amplitude ratio. Default value is 0.

stop_periods

Set the count for trimming silence from the end of audio.
To remove silence from the middle of a file, specify a stop_periods
that is negative. This value is then treated as a positive value and is
used to indicate the effect should restart processing as specified by
start_periods, making it suitable for removing periods of silence
in the middle of the audio.
Default value is 0.

stop_duration

Specify a duration of silence that must exist before audio is not copied any
more. By specifying a higher duration, silence that is wanted can be left in
the audio.
Default value is 0.

stop_threshold

This is the same as start_threshold but for trimming silence from
the end of audio.
Can be specified in dB (in case "dB" is appended to the specified value)
or amplitude ratio. Default value is 0.

leave_silence

This indicates that stop_duration length of audio should be left intact
at the beginning of each period of silence.
For example, if you want to remove long pauses between words but do not want
to remove the pauses completely. Default value is 0.

detection

Set how is silence detected. Can be rms or peak. Second is faster
and works better with digital silence which is exactly 0.
Default value is rms.

window

Set ratio used to calculate size of window for detecting silence.
Default value is 0.02. Allowed range is from 0 to 10.

The following example shows how this filter can be used to start a recording
that does not contain the delay at the start which usually occurs between
pressing the record button and the start of the performance:

silenceremove=1:5:0.02

Trim all silence encountered from beginning to end where there is more than 1
second of silence in audio:

SOFAlizer uses head-related transfer functions (HRTFs) to create virtual
loudspeakers around the user for binaural listening via headphones (audio
formats up to 9 channels supported).
The HRTFs are stored in SOFA files (see http://www.sofacoustics.org/ for a database).
SOFAlizer is developed at the Acoustics Research Institute (ARI) of the
Austrian Academy of Sciences.

To enable compilation of this filter you need to configure FFmpeg with
--enable-netcdf.

The filter accepts the following options:

sofa

Set the SOFA file used for rendering.

gain

Set gain applied to audio. Value is in dB. Default is 0.

rotation

Set rotation of virtual loudspeakers in deg. Default is 0.

elevation

Set elevation of virtual speakers in deg. Default is 0.

radius

Set distance in meters between loudspeakers and the listener with near-field
HRTFs. Default is 1.

type

Set processing type. Can be time or freq. time is
processing audio in time domain which is slow.
freq is processing audio in frequency domain which is fast.
Default is freq.

speakers

Set custom positions of virtual loudspeakers. Syntax for this option is:
<CH> <AZIM> <ELEV>[|<CH> <AZIM> <ELEV>|...].
Each virtual loudspeaker is described with short channel name following with
azimuth and elevation in degreees.
Each virtual loudspeaker description is separated by ’|’.
For example to override front left and front right channel positions use:
’speakers=FL 45 15|FR 345 15’.
Descriptions with unrecognised channel names are ignored.

This filter has some handy utilities to manage stereo signals, for converting
M/S stereo recordings to L/R signal while having control over the parameters
or spreading the stereo image of master track.

The filter accepts the following options:

level_in

Set input level before filtering for both channels. Defaults is 1.
Allowed range is from 0.015625 to 64.

level_out

Set output level after filtering for both channels. Defaults is 1.
Allowed range is from 0.015625 to 64.

balance_in

Set input balance between both channels. Default is 0.
Allowed range is from -1 to 1.

balance_out

Set output balance between both channels. Default is 0.
Allowed range is from -1 to 1.

Boost or cut treble (upper) frequencies of the audio using a two-pole
shelving filter with a response similar to that of a standard
hi-fi’s tone-controls. This is also known as shelving equalisation (EQ).

The filter accepts the following options:

gain, g

Give the gain at whichever is the lower of ~22 kHz and the
Nyquist frequency. Its useful range is about -20 (for a large cut)
to +20 (for a large boost). Beware of clipping when using a positive gain.

frequency, f

Set the filter’s central frequency and so can be used
to extend or reduce the frequency range to be boosted or cut.
The default value is 3000 Hz.

Modulation frequency in Hertz. Modulation frequencies in the subharmonic range
(20 Hz or lower) will result in a tremolo effect.
This filter may also be used as a ring modulator by specifying
a modulation frequency higher than 20 Hz.
Range is 0.1 - 20000.0. Default value is 5.0 Hz.

d

Depth of modulation as a percentage. Range is 0.0 - 1.0.
Default value is 0.5.

The filter has no parameters. The input is not modified. Statistics about
the volume will be printed in the log when the input stream end is reached.

In particular it will show the mean volume (root mean square), maximum
volume (on a per-sample basis), and the beginning of a histogram of the
registered volume values (from the maximum value to a cumulated 1/1000 of
the samples).

This source is mainly intended for a programmatic use, in particular
through the interface defined in libavfilter/asrc_abuffer.h.

It accepts the following parameters:

time_base

The timebase which will be used for timestamps of submitted frames. It must be
either a floating-point number or in numerator/denominator form.

sample_rate

The sample rate of the incoming audio buffers.

sample_fmt

The sample format of the incoming audio buffers.
Either a sample format name or its corresponding integer representation from
the enum AVSampleFormat in libavutil/samplefmt.h

channel_layout

The channel layout of the incoming audio buffers.
Either a channel layout name from channel_layout_map in
libavutil/channel_layout.c or its corresponding integer representation
from the AV_CH_LAYOUT_* macros in libavutil/channel_layout.h

channels

The number of channels of the incoming audio buffers.
If both channels and channel_layout are specified, then they
must be consistent.

will instruct the source to accept planar 16bit signed stereo at 44100Hz.
Since the sample format with name "s16p" corresponds to the number
6 and the "stereo" channel layout corresponds to the value 0x3, this is
equivalent to:

This source accepts in input one or more expressions (one for each
channel), which are evaluated and used to generate a corresponding
audio signal.

This source accepts the following options:

exprs

Set the ’|’-separated expressions list for each separate channel. In case the
channel_layout option is not specified, the selected channel layout
depends on the number of provided expressions. Otherwise the last
specified expression is applied to the remaining output channels.

channel_layout, c

Set the channel layout. The number of channels in the specified layout
must be equal to the number of specified expressions.

The null audio source, return unprocessed audio frames. It is mainly useful
as a template and to be employed in analysis / debugging tools, or as
the source for filters which ignore the input data (for example the sox
synth filter).

This source accepts the following options:

channel_layout, cl

Specifies the channel layout, and can be either an integer or a string
representing a channel layout. The default value of channel_layout
is "stereo".

Check the channel_layout_map definition in
libavutil/channel_layout.c for the mapping between strings and
channel layout values.

Add or replace the alpha component of the primary input with the
grayscale value of a second input. This is intended for use with
alphaextract to allow the transmission or storage of frame
sequences that have alpha in a format that doesn’t support an alpha
channel.

For example, to reconstruct full frames from a normal YUV-encoded video
and a separate video created with alphaextract, you might use:

movie=in_alpha.mkv [alpha]; [in][alpha] alphamerge [out]

Since this filter is designed for reconstruction, it operates on frame
sequences without considering timestamps, and terminates when either
input reaches end of stream. This will cause problems if your encoding
pipeline drops frames. If you’re trying to apply an image as an
overlay to a video stream, consider the overlay filter instead.

Detect video intervals that are (almost) completely black. Can be
useful to detect chapter transitions, commercials, or invalid
recordings. Output lines contains the time for the start, end and
duration of the detected black interval expressed in seconds.

In order to display the output lines, you need to set the loglevel at
least to the AV_LOG_INFO value.

The filter accepts the following options:

black_min_duration, d

Set the minimum detected black duration expressed in seconds. It must
be a non-negative floating point number.

Default value is 2.0.

picture_black_ratio_th, pic_th

Set the threshold for considering a picture "black".
Express the minimum value for the ratio:

nb_black_pixels / nb_pixels

for which a picture is considered black.
Default value is 0.98.

pixel_black_th, pix_th

Set the threshold for considering a pixel "black".

The threshold expresses the maximum pixel luminance value for which a
pixel is considered "black". The provided value is scaled according to
the following equation:

Detect frames that are (almost) completely black. Can be useful to
detect chapter transitions or commercials. Output lines consist of
the frame number of the detected frame, the percentage of blackness,
the position in the file if known or -1 and the timestamp in seconds.

In order to display the output lines, you need to set the loglevel at
least to the AV_LOG_INFO value.

This filter exports frame metadata lavfi.blackframe.pblack.
The value represents the percentage of pixels in the picture that
are below the threshold value.

It accepts the following parameters:

amount

The percentage of the pixels that have to be below the threshold; it defaults to
98.

threshold, thresh

The threshold below which a pixel value is considered black; it defaults to
32.

The blend filter takes two input streams and outputs one
stream, the first input is the "top" layer and second input is
"bottom" layer. By default, the output terminates when the longest input terminates.

The tblend (time blend) filter takes two consecutive frames
from one single stream, and outputs the result obtained by blending
the new frame on top of the old frame.

A description of the accepted options follows.

c0_mode

c1_mode

c2_mode

c3_mode

all_mode

Set blend mode for specific pixel component or all pixel components in case
of all_mode. Default value is normal.

Available values for component modes are:

‘addition’

‘addition128’

‘and’

‘average’

‘burn’

‘darken’

‘difference’

‘difference128’

‘divide’

‘dodge’

‘freeze’

‘exclusion’

‘glow’

‘hardlight’

‘hardmix’

‘heat’

‘lighten’

‘linearlight’

‘multiply’

‘multiply128’

‘negation’

‘normal’

‘or’

‘overlay’

‘phoenix’

‘pinlight’

‘reflect’

‘screen’

‘softlight’

‘subtract’

‘vividlight’

‘xor’

c0_opacity

c1_opacity

c2_opacity

c3_opacity

all_opacity

Set blend opacity for specific pixel component or all pixel components in case
of all_opacity. Only used in combination with pixel component blend modes.

c0_expr

c1_expr

c2_expr

c3_expr

all_expr

Set blend expression for specific pixel component or all pixel components in case
of all_expr. Note that related mode options will be ignored if those are set.

The expressions can use the following variables:

N

The sequential number of the filtered frame, starting from 0.

X

Y

the coordinates of the current sample

W

H

the width and height of currently filtered plane

SW

SH

Width and height scale depending on the currently filtered plane. It is the
ratio between the corresponding luma plane number of pixels and the current
plane ones. E.g. for YUV4:2:0 the values are 1,1 for the luma plane, and
0.5,0.5 for chroma planes.

T

Time of the current frame, expressed in seconds.

TOP, A

Value of pixel component at current location for first video frame (top layer).

BOTTOM, B

Value of pixel component at current location for second video frame (bottom layer).

shortest

Force termination when the shortest input terminates. Default is
0. This option is only defined for the blend filter.

repeatlast

Continue applying the last bottom frame after the end of the stream. A value of
0 disable the filter after the last frame of the bottom layer is reached.
Default is 1. This option is only defined for the blend filter.

Convert colorspace, transfer characteristics or color primaries.
Input video needs to have an even size.

The filter accepts the following options:

all

Specify all color properties at once.

The accepted values are:

‘bt470m’

BT.470M

‘bt470bg’

BT.470BG

‘bt601-6-525’

BT.601-6 525

‘bt601-6-625’

BT.601-6 625

‘bt709’

BT.709

‘smpte170m’

SMPTE-170M

‘smpte240m’

SMPTE-240M

‘bt2020’

BT.2020

space

Specify output colorspace.

The accepted values are:

‘bt709’

BT.709

‘fcc’

FCC

‘bt470bg’

BT.470BG or BT.601-6 625

‘smpte170m’

SMPTE-170M or BT.601-6 525

‘smpte240m’

SMPTE-240M

‘ycgco’

YCgCo

‘bt2020ncl’

BT.2020 with non-constant luminance

trc

Specify output transfer characteristics.

The accepted values are:

‘bt709’

BT.709

‘bt470m’

BT.470M

‘bt470bg’

BT.470BG

‘gamma22’

Constant gamma of 2.2

‘gamma28’

Constant gamma of 2.8

‘smpte170m’

SMPTE-170M, BT.601-6 625 or BT.601-6 525

‘smpte240m’

SMPTE-240M

‘srgb’

SRGB

‘iec61966-2-1’

iec61966-2-1

‘iec61966-2-4’

iec61966-2-4

‘xvycc’

xvycc

‘bt2020-10’

BT.2020 for 10-bits content

‘bt2020-12’

BT.2020 for 12-bits content

primaries

Specify output color primaries.

The accepted values are:

‘bt709’

BT.709

‘bt470m’

BT.470M

‘bt470bg’

BT.470BG or BT.601-6 625

‘smpte170m’

SMPTE-170M or BT.601-6 525

‘smpte240m’

SMPTE-240M

‘film’

film

‘smpte431’

SMPTE-431

‘smpte432’

SMPTE-432

‘bt2020’

BT.2020

range

Specify output color range.

The accepted values are:

‘tv’

TV (restricted) range

‘mpeg’

MPEG (restricted) range

‘pc’

PC (full) range

‘jpeg’

JPEG (full) range

format

Specify output color format.

The accepted values are:

‘yuv420p’

YUV 4:2:0 planar 8-bits

‘yuv420p10’

YUV 4:2:0 planar 10-bits

‘yuv420p12’

YUV 4:2:0 planar 12-bits

‘yuv422p’

YUV 4:2:2 planar 8-bits

‘yuv422p10’

YUV 4:2:2 planar 10-bits

‘yuv422p12’

YUV 4:2:2 planar 12-bits

‘yuv444p’

YUV 4:4:4 planar 8-bits

‘yuv444p10’

YUV 4:4:4 planar 10-bits

‘yuv444p12’

YUV 4:4:4 planar 12-bits

fast

Do a fast conversion, which skips gamma/primary correction. This will take
significantly less CPU, but will be mathematically incorrect. To get output
compatible with that produced by the colormatrix filter, use fast=1.

The filter converts the transfer characteristics, color space and color
primaries to the specified user values. The output value, if not specified,
is set to a default value based on the "all" property. If that property is
also not specified, the filter will log an error. The output color range and
format default to the same value as the input color range and format. The
input transfer characteristics, color space, color primaries and color range
should be set on the input data. If any of these are missing, the filter will
log an error and no conversion will take place.

Hardware acceleration is based on an OpenGL context. Usually, this means it is
processed by video hardware. However, software-based OpenGL implementations
exist which means there is no guarantee for hardware processing. It depends on
the respective OSX.

There are many filters and image generators provided by Apple that come with a
large variety of options. The filter has to be referenced by its name along
with its options.

The coreimage filter accepts the following options:

list_filters

List all available filters and generators along with all their respective
options as well as possible minimum and maximum values along with the default
values.

list_filters=true

filter

Specify all filters by their respective name and options.
Use list_filters to determine all valid filter names and options.
Numerical options are specified by a float value and are automatically clamped
to their respective value range. Vector and color options have to be specified
by a list of space separated float values. Character escaping has to be done.
A special option name default is available to use default options for a
filter.

It is required to specify either default or at least one of the filter options.
All omitted options are used with their default values.
The syntax of the filter string is as follows:

Specify a rectangle where the output of the filter chain is copied into the
input image. It is given by a list of space separated float values:

output_rect=x\ y\ width\ height

If not given, the output rectangle equals the dimensions of the input image.
The output rectangle is automatically cropped at the borders of the input
image. Negative values are valid for each component.

output_rect=25\ 25\ 100\ 100

Several filters can be chained for successive processing without GPU-HOST
transfers allowing for fast processing of complex filter chains.
Currently, only filters with zero (generators) or exactly one (filters) input
image and one output image are supported. Also, transition filters are not yet
usable as intended.

Some filters generate output images with additional padding depending on the
respective filter kernel. The padding is automatically removed to ensure the
filter output has the same size as the input image.

For image generators, the size of the output image is determined by the
previous output image of the filter chain or the input image of the whole
filterchain, respectively. The generators do not use the pixel information of
this image to generate their output. However, the generated output is
blended onto this image, resulting in partial or complete coverage of the
output image.

The coreimagesrc video source can be used for generating input images
which are directly fed into the filter chain. By using it, providing input
images by another video source or an input video is not required.

The width of the output video. It defaults to iw.
This expression is evaluated only once during the filter
configuration, or when the ‘w’ or ‘out_w’ command is sent.

h, out_h

The height of the output video. It defaults to ih.
This expression is evaluated only once during the filter
configuration, or when the ‘h’ or ‘out_h’ command is sent.

x

The horizontal position, in the input video, of the left edge of the output
video. It defaults to (in_w-out_w)/2.
This expression is evaluated per-frame.

y

The vertical position, in the input video, of the top edge of the output video.
It defaults to (in_h-out_h)/2.
This expression is evaluated per-frame.

keep_aspect

If set to 1 will force the output display aspect ratio
to be the same of the input, by changing the output sample aspect
ratio. It defaults to 0.

exact

Enable exact cropping. If enabled, subsampled videos will be cropped at exact
width/height/x/y as specified and will not be rounded to nearest smaller value.
It defaults to 0.

The out_w, out_h, x, y parameters are
expressions containing the following constants:

x

y

The computed values for x and y. They are evaluated for
each new frame.

in_w

in_h

The input width and height.

iw

ih

These are the same as in_w and in_h.

out_w

out_h

The output (cropped) width and height.

ow

oh

These are the same as out_w and out_h.

a

same as iw / ih

sar

input sample aspect ratio

dar

input display aspect ratio, it is the same as (iw / ih) * sar

hsub

vsub

horizontal and vertical chroma subsample values. For example for the
pixel format "yuv422p" hsub is 2 and vsub is 1.

n

The number of the input frame, starting from 0.

pos

the position in the file of the input frame, NAN if unknown

t

The timestamp expressed in seconds. It’s NAN if the input timestamp is unknown.

The expression for out_w may depend on the value of out_h,
and the expression for out_h may depend on out_w, but they
cannot depend on x and y, as x and y are
evaluated after out_w and out_h.

The x and y parameters specify the expressions for the
position of the top-left corner of the output (non-cropped) area. They
are evaluated for each frame. If the evaluated value is not valid, it
is approximated to the nearest valid value.

The expression for x may depend on y, and the expression
for y may depend on x.

It calculates the necessary cropping parameters and prints the
recommended parameters via the logging system. The detected dimensions
correspond to the non-black area of the input video.

It accepts the following parameters:

limit

Set higher black value threshold, which can be optionally specified
from nothing (0) to everything (255 for 8-bit based formats). An intensity
value greater to the set value is considered non-black. It defaults to 24.
You can also specify a value between 0.0 and 1.0 which will be scaled depending
on the bitdepth of the pixel format.

round

The value which the width/height should be divisible by. It defaults to
16. The offset is automatically adjusted to center the video. Use 2 to
get only even dimensions (needed for 4:2:2 video). 16 is best when
encoding to most video codecs.

reset_count, reset

Set the counter that determines after how many frames cropdetect will
reset the previously detected largest video area and start over to
detect the current optimal crop area. Default value is 0.

This can be useful when channel logos distort the video area. 0
indicates ’never reset’, and returns the largest area encountered during
playback.

This filter is similar to the Adobe Photoshop and GIMP curves tools. Each
component (red, green and blue) has its values defined by N key points
tied from each other using a smooth curve. The x-axis represents the pixel
values from the input frame, and the y-axis the new pixel values to be set for
the output frame.

By default, a component curve is defined by the two points (0;0) and
(1;1). This creates a straight line where each original pixel value is
"adjusted" to its own value, which means no change to the image.

The filter allows you to redefine these two points and add some more. A new
curve (using a natural cubic spline interpolation) will be define to pass
smoothly through all these new coordinates. The new defined points needs to be
strictly increasing over the x-axis, and their x and y values must
be in the [0;1] interval. If the computed curves happened to go outside
the vector spaces, the values will be clipped accordingly.

The filter accepts the following options:

preset

Select one of the available color presets. This option can be used in addition
to the r, g, b parameters; in this case, the later
options takes priority on the preset values.
Available presets are:

‘none’

‘color_negative’

‘cross_process’

‘darker’

‘increase_contrast’

‘lighter’

‘linear_contrast’

‘medium_contrast’

‘negative’

‘strong_contrast’

‘vintage’

Default is none.

master, m

Set the master key points. These points will define a second pass mapping. It
is sometimes called a "luminance" or "value" mapping. It can be used with
r, g, b or all since it acts like a
post-processing LUT.

red, r

Set the key points for the red component.

green, g

Set the key points for the green component.

blue, b

Set the key points for the blue component.

all

Set the key points for all components (not including master).
Can be used in addition to the other key points component
options. In this case, the unset component(s) will fallback on this
all setting.

psfile

Specify a Photoshop curves file (.acv) to import the settings from.

plot

Save Gnuplot script of the curves in specified file.

To avoid some filtergraph syntax conflicts, each key points list need to be
defined using the following syntax: x0/y0 x1/y1 x2/y2 ....

This sigma defines a hard threshold of 3 * sigma; every DCT
coefficient (absolute value) below this threshold with be dropped.

If you need a more advanced filtering, see expr.

Default is 0.

overlap

Set number overlapping pixels for each block. Since the filter can be slow, you
may want to reduce this value, at the cost of a less effective filter and the
risk of various artefacts.

If the overlapping value doesn’t permit processing the whole input width or
height, a warning will be displayed and according borders won’t be denoised.

Default value is blocksize-1, which is the best possible setting.

expr, e

Set the coefficient factor expression.

For each coefficient of a DCT block, this expression will be evaluated as a
multiplier value for the coefficient.

If this is option is set, the sigma option will be ignored.

The absolute value of the coefficient can be accessed through the c
variable.

n

Set the blocksize using the number of bits. 1<<n defines the
blocksize, which is the width and height of the processed blocks.

The default value is 3 (8x8) and can be raised to 4 for a
blocksize of 16x16. Note that changing this setting has huge consequences
on the speed processing. Also, a larger block size does not necessarily means a
better de-noising.

Remove banding artifacts from input video.
It works by replacing banded pixels with average value of referenced pixels.

The filter accepts the following options:

1thr

2thr

3thr

4thr

Set banding detection threshold for each plane. Default is 0.02.
Valid range is 0.00003 to 0.5.
If difference between current pixel and reference pixel is less than threshold,
it will be considered as banded.

range, r

Banding detection range in pixels. Default is 16. If positive, random number
in range 0 to set value will be used. If negative, exact absolute value
will be used.
The range defines square of four pixels around current pixel.

direction, d

Set direction in radians from which four pixel will be compared. If positive,
random direction from 0 to set direction will be picked. If negative, exact of
absolute value will be picked. For example direction 0, -PI or -2*PI radians
will pick only pixels on same row and -PI/2 will pick only pixels on same
column.

blur

If enabled, current pixel is compared with average value of all four
surrounding pixels. The default is enabled. If disabled current pixel is
compared with all four surrounding pixels. The pixel is considered banded
if only all four differences with surrounding pixels are less than threshold.

Set the number of frames from which one will be dropped. Setting this to
N means one frame in every batch of N frames will be dropped.
Default is 5.

dupthresh

Set the threshold for duplicate detection. If the difference metric for a frame
is less than or equal to this value, then it is declared as duplicate. Default
is 1.1

scthresh

Set scene change threshold. Default is 15.

blockx

blocky

Set the size of the x and y-axis blocks used during metric calculations.
Larger blocks give better noise suppression, but also give worse detection of
small movements. Must be a power of two. Default is 32.

ppsrc

Mark main input as a pre-processed input and activate clean source input
stream. This allows the input to be pre-processed with various filters to help
the metrics calculation while keeping the frame selection lossless. When set to
1, the first stream is for the pre-processed input, and the second
stream is the clean source from where the kept frames are chosen. Default is
0.

chroma

Set whether or not chroma is considered in the metric calculations. Default is
1.

Judder can be introduced, for instance, by pullup filter. If the original
source was partially telecined content then the output of pullup,dejudder
will have a variable frame rate. May change the recorded frame rate of the
container. Aside from that change, this filter will not affect constant frame
rate video.

Suppress a TV station logo by a simple interpolation of the surrounding
pixels. Just set a rectangle covering the logo and watch it disappear
(and sometimes something even uglier appear - your mileage may vary).

It accepts the following parameters:

x

y

Specify the top left corner coordinates of the logo. They must be
specified.

w

h

Specify the width and height of the logo to clear. They must be
specified.

band, t

Specify the thickness of the fuzzy edge of the rectangle (added to
w and h). The default value is 1. This option is
deprecated, setting higher values should no longer be necessary and
is not recommended.

show

When set to 1, a green rectangle is drawn on the screen to simplify
finding the right x, y, w, and h parameters.
The default value is 0.

The rectangle is drawn on the outermost pixels which will be (partly)
replaced with interpolated values. The values of the next pixels
immediately outside this rectangle in each direction will be used to
compute the interpolated pixel values inside the rectangle.

Attempt to fix small changes in horizontal and/or vertical shift. This
filter helps remove camera shake from hand-holding a camera, bumping a
tripod, moving on a vehicle, etc.

The filter accepts the following options:

x

y

w

h

Specify a rectangular area where to limit the search for motion
vectors.
If desired the search for motion vectors can be limited to a
rectangular area of the frame defined by its top left corner, width
and height. These parameters have the same meaning as the drawbox
filter which can be used to visualise the position of the bounding
box.

This is useful when simultaneous movement of subjects within the frame
might be confused for camera motion by the motion vector search.

If any or all of x, y, w and h are set to -1
then the full frame is used. This allows later options to be set
without specifying the bounding box for the motion vector search.

Default - search the whole frame.

rx

ry

Specify the maximum extent of movement in x and y directions in the
range 0-64 pixels. Default 16.

edge

Specify how to generate pixels to fill blanks at the edge of the
frame. Available values are:

‘blank, 0’

Fill zeroes at blank locations

‘original, 1’

Original image at blank locations

‘clamp, 2’

Extruded edge value at blank locations

‘mirror, 3’

Mirrored edge at blank locations

Default value is ‘mirror’.

blocksize

Specify the blocksize to use for motion search. Range 4-128 pixels,
default 8.

contrast

Specify the contrast threshold for blocks. Only blocks with more than
the specified contrast (difference between darkest and lightest
pixels) will be considered. Range 1-255, default 125.

search

Specify the search strategy. Available values are:

‘exhaustive, 0’

Set exhaustive search

‘less, 1’

Set less exhaustive search.

Default value is ‘exhaustive’.

filename

If set then a detailed log of the motion search is written to the
specified file.

opencl

If set to 1, specify using OpenCL capabilities, only available if
FFmpeg was configured with --enable-opencl. Default value is 0.

It takes three input streams and outputs one stream, the first input is the
source, and second and third input are displacement maps.

The second input specifies how much to displace pixels along the
x-axis, while the third input specifies how much to displace pixels
along the y-axis.
If one of displacement map streams terminates, last frame from that
displacement map will be used.

Note that once generated, displacements maps can be reused over and over again.

A description of the accepted options follows.

edge

Set displace behavior for pixels that are out of range.

Available values are:

‘blank’

Missing pixels are replaced by black pixels.

‘smear’

Adjacent pixels will spread out to replace missing pixels.

‘wrap’

Out of range pixels are wrapped so they point to pixels of other side.

The expressions which specify the top left corner coordinates of the box. It defaults to 0.

width, w

height, h

The expressions which specify the width and height of the box; if 0 they are interpreted as
the input width and height. It defaults to 0.

color, c

Specify the color of the box to write. For the general syntax of this option,
check the "Color" section in the ffmpeg-utils manual. If the special
value invert is used, the box edge color is the same as the
video with inverted luma.

thickness, t

The expression which sets the thickness of the box edge. Default value is 3.

See below for the list of accepted constants.

The parameters for x, y, w and h and t are expressions containing the
following constants:

dar

The input display aspect ratio, it is the same as (w / h) * sar.

hsub

vsub

horizontal and vertical chroma subsample values. For example for the
pixel format "yuv422p" hsub is 2 and vsub is 1.

in_h, ih

in_w, iw

The input width and height.

sar

The input sample aspect ratio.

x

y

The x and y offset coordinates where the box is drawn.

w

h

The width and height of the drawn box.

t

The thickness of the drawn box.

These constants allow the x, y, w, h and t expressions to refer to
each other, so you may for example specify y=x/dar or h=w/dar.

The expressions which specify the coordinates of some point of grid intersection (meant to configure offset). Both default to 0.

width, w

height, h

The expressions which specify the width and height of the grid cell, if 0 they are interpreted as the
input width and height, respectively, minus thickness, so image gets
framed. Default to 0.

color, c

Specify the color of the grid. For the general syntax of this option,
check the "Color" section in the ffmpeg-utils manual. If the special
value invert is used, the grid color is the same as the
video with inverted luma.

thickness, t

The expression which sets the thickness of the grid line. Default value is 1.

See below for the list of accepted constants.

The parameters for x, y, w and h and t are expressions containing the
following constants:

dar

The input display aspect ratio, it is the same as (w / h) * sar.

hsub

vsub

horizontal and vertical chroma subsample values. For example for the
pixel format "yuv422p" hsub is 2 and vsub is 1.

in_h, ih

in_w, iw

The input grid cell width and height.

sar

The input sample aspect ratio.

x

y

The x and y coordinates of some point of grid intersection (meant to configure offset).

w

h

The width and height of the drawn cell.

t

The thickness of the drawn cell.

These constants allow the x, y, w, h and t expressions to refer to
each other, so you may for example specify y=x/dar or h=w/dar.

Draw a text string or text from a specified file on top of a video, using the
libfreetype library.

To enable compilation of this filter, you need to configure FFmpeg with
--enable-libfreetype.
To enable default font fallback and the font option you need to
configure FFmpeg with --enable-libfontconfig.
To enable the text_shaping option, you need to configure FFmpeg with
--enable-libfribidi.

Used to draw a box around text using the background color.
The value must be either 1 (enable) or 0 (disable).
The default value of box is 0.

boxborderw

Set the width of the border to be drawn around the box using boxcolor.
The default value of boxborderw is 0.

boxcolor

The color to be used for drawing box around text. For the syntax of this
option, check the "Color" section in the ffmpeg-utils manual.

The default value of boxcolor is "white".

borderw

Set the width of the border to be drawn around the text using bordercolor.
The default value of borderw is 0.

bordercolor

Set the color to be used for drawing border around text. For the syntax of this
option, check the "Color" section in the ffmpeg-utils manual.

The default value of bordercolor is "black".

expansion

Select how the text is expanded. Can be either none,
strftime (deprecated) or
normal (default). See the Text expansion section
below for details.

fix_bounds

If true, check and fix text coords to avoid clipping.

fontcolor

The color to be used for drawing fonts. For the syntax of this option, check
the "Color" section in the ffmpeg-utils manual.

The default value of fontcolor is "black".

fontcolor_expr

String which is expanded the same way as text to obtain dynamic
fontcolor value. By default this option has empty value and is not
processed. When this option is set, it overrides fontcolor option.

font

The font family to be used for drawing text. By default Sans.

fontfile

The font file to be used for drawing text. The path must be included.
This parameter is mandatory if the fontconfig support is disabled.

draw

This option does not exist, please see the timeline system

alpha

Draw the text applying alpha blending. The value can
be a number between 0.0 and 1.0.
The expression accepts the same variables x, y as well.
The default value is 1.
Please see fontcolor_expr.

fontsize

The font size to be used for drawing text.
The default value of fontsize is 16.

text_shaping

If set to 1, attempt to shape the text (for example, reverse the order of
right-to-left text and join Arabic characters) before drawing it.
Otherwise, just draw the text exactly as given.
By default 1 (if supported).

ft_load_flags

The flags to be used for loading the fonts.

The flags map the corresponding flags supported by libfreetype, and are
a combination of the following values:

default

no_scale

no_hinting

render

no_bitmap

vertical_layout

force_autohint

crop_bitmap

pedantic

ignore_global_advance_width

no_recurse

ignore_transform

monochrome

linear_design

no_autohint

Default value is "default".

For more information consult the documentation for the FT_LOAD_*
libfreetype flags.

shadowcolor

The color to be used for drawing a shadow behind the drawn text. For the
syntax of this option, check the "Color" section in the ffmpeg-utils manual.

The default value of shadowcolor is "black".

shadowx

shadowy

The x and y offsets for the text shadow position with respect to the
position of the text. They can be either positive or negative
values. The default value for both is "0".

start_number

The starting frame number for the n/frame_num variable. The default value
is "0".

tabsize

The size in number of spaces to use for rendering the tab.
Default value is 4.

timecode

Set the initial timecode representation in "hh:mm:ss[:;.]ff"
format. It can be used with or without text parameter. timecode_rate
option must be specified.

timecode_rate, rate, r

Set the timecode frame rate (timecode only).

text

The text string to be drawn. The text must be a sequence of UTF-8
encoded characters.
This parameter is mandatory if no file is specified with the parameter
textfile.

textfile

A text file containing text to be drawn. The text must be a sequence
of UTF-8 encoded characters.

This parameter is mandatory if no text string is specified with the
parameter text.

If both text and textfile are specified, an error is thrown.

reload

If set to 1, the textfile will be reloaded before each frame.
Be sure to update it atomically, or it may be read partially, or even fail.

x

y

The expressions which specify the offsets where text will be drawn
within the video frame. They are relative to the top/left border of the
output image.

The default value of x and y is "0".

See below for the list of accepted constants and functions.

The parameters for x and y are expressions containing the
following constants and functions:

dar

input display aspect ratio, it is the same as (w / h) * sar

hsub

vsub

horizontal and vertical chroma subsample values. For example for the
pixel format "yuv422p" hsub is 2 and vsub is 1.

line_h, lh

the height of each text line

main_h, h, H

the input height

main_w, w, W

the input width

max_glyph_a, ascent

the maximum distance from the baseline to the highest/upper grid
coordinate used to place a glyph outline point, for all the rendered
glyphs.
It is a positive value, due to the grid’s orientation with the Y axis
upwards.

max_glyph_d, descent

the maximum distance from the baseline to the lowest grid coordinate
used to place a glyph outline point, for all the rendered glyphs.
This is a negative value, due to the grid’s orientation, with the Y axis
upwards.

max_glyph_h

maximum glyph height, that is the maximum height for all the glyphs
contained in the rendered text, it is equivalent to ascent -
descent.

max_glyph_w

maximum glyph width, that is the maximum width for all the glyphs
contained in the rendered text

n

the number of input frame, starting from 0

rand(min, max)

return a random number included between min and max

sar

The input sample aspect ratio.

t

timestamp expressed in seconds, NAN if the input timestamp is unknown

text_h, th

the height of the rendered text

text_w, tw

the width of the rendered text

x

y

the x and y offset coordinates where the text is drawn.

These parameters allow the x and y expressions to refer
each other, so you can for example specify y=x/dar.

If expansion is set to strftime,
the filter recognizes strftime() sequences in the provided text and
expands them accordingly. Check the documentation of strftime(). This
feature is deprecated.

If expansion is set to none, the text is printed verbatim.

If expansion is set to normal (which is the default),
the following expansion mechanism is used.

The backslash character ‘\’, followed by any character, always expands to
the second character.

Sequences of the form %{...} are expanded. The text between the
braces is a function name, possibly followed by arguments separated by ’:’.
If the arguments contain special characters or delimiters (’:’ or ’}’),
they should be escaped.

Note that they probably must also be escaped as the value for the
text option in the filter argument string and as the filter
argument in the filtergraph description, and possibly also for the shell,
that makes up to four levels of escaping; using a text file avoids these
problems.

The following functions are available:

expr, e

The expression evaluation result.

It must take one argument specifying the expression to be evaluated,
which accepts the same constants and functions as the x and
y values. Note that not all constants should be used, for
example the text size is not known when evaluating the expression, so
the constants text_w and text_h will have an undefined
value.

expr_int_format, eif

Evaluate the expression’s value and output as formatted integer.

The first argument is the expression to be evaluated, just as for the expr function.
The second argument specifies the output format. Allowed values are ‘x’,
‘X’, ‘d’ and ‘u’. They are treated exactly as in the
printf function.
The third parameter is optional and sets the number of positions taken by the output.
It can be used to add padding with zeros from the left.

gmtime

The time at which the filter is running, expressed in UTC.
It can accept an argument: a strftime() format string.

localtime

The time at which the filter is running, expressed in the local time zone.
It can accept an argument: a strftime() format string.

metadata

Frame metadata. Takes one or two arguments.

The first argument is mandatory and specifies the metadata key.

The second argument is optional and specifies a default value, used when the
metadata key is not found or empty.

n, frame_num

The frame number, starting from 0.

pict_type

A 1 character description of the current picture type.

pts

The timestamp of the current frame.
It can take up to three arguments.

The first argument is the format of the timestamp; it defaults to flt
for seconds as a decimal number with microsecond accuracy; hms stands
for a formatted [-]HH:MM:SS.mmm timestamp with millisecond accuracy.
gmtime stands for the timestamp of the frame formatted as UTC time;
localtime stands for the timestamp of the frame formatted as
local time zone time.

The second argument is an offset added to the timestamp.

If the format is set to localtime or gmtime,
a third argument may be supplied: a strftime() format string.
By default, YYYY-MM-DD HH:MM:SS format will be used.

Draw ’Test Text’ with font FreeSerif of size 24 at position x=100
and y=50 (counting from the top-left corner of the screen), text is
yellow with a red box around it. Both the text and the box have an
opacity of 20%.

Set the contrast expression. The value must be a float value in range
-2.0 to 2.0. The default value is "1".

brightness

Set the brightness expression. The value must be a float value in
range -1.0 to 1.0. The default value is "0".

saturation

Set the saturation expression. The value must be a float in
range 0.0 to 3.0. The default value is "1".

gamma

Set the gamma expression. The value must be a float in range
0.1 to 10.0. The default value is "1".

gamma_r

Set the gamma expression for red. The value must be a float in
range 0.1 to 10.0. The default value is "1".

gamma_g

Set the gamma expression for green. The value must be a float in range
0.1 to 10.0. The default value is "1".

gamma_b

Set the gamma expression for blue. The value must be a float in range
0.1 to 10.0. The default value is "1".

gamma_weight

Set the gamma weight expression. It can be used to reduce the effect
of a high gamma value on bright image areas, e.g. keep them from
getting overamplified and just plain white. The value must be a float
in range 0.0 to 1.0. A value of 0.0 turns the
gamma correction all the way down while 1.0 leaves it at its
full strength. Default is "1".

eval

Set when the expressions for brightness, contrast, saturation and
gamma expressions are evaluated.

It accepts the following values:

‘init’

only evaluate expressions once during the filter initialization or
when a command is processed

‘frame’

evaluate expressions for each incoming frame

Default value is ‘init’.

The expressions accept the following parameters:

n

frame count of the input frame starting from 0

pos

byte position of the corresponding packet in the input file, NAN if
unspecified

The effect type can be either "in" for a fade-in, or "out" for a fade-out
effect.
Default is in.

start_frame, s

Specify the number of the frame to start applying the fade
effect at. Default is 0.

nb_frames, n

The number of frames that the fade effect lasts. At the end of the
fade-in effect, the output video will have the same intensity as the input video.
At the end of the fade-out transition, the output video will be filled with the
selected color.
Default is 25.

alpha

If set to 1, fade only alpha channel, if one exists on the input.
Default value is 0.

start_time, st

Specify the timestamp (in seconds) of the frame to start to apply the fade
effect. If both start_frame and start_time are specified, the fade will start at
whichever comes last. Default is 0.

duration, d

The number of seconds for which the fade effect has to last. At the end of the
fade-in effect the output video will have the same intensity as the input video,
at the end of the fade-out transition the output video will be filled with the
selected color.
If both duration and nb_frames are specified, duration is used. Default is 0
(nb_frames is used by default).

Create new frames by copying the top and bottom fields from surrounding frames
supplied as numbers by the hint file.

hint

Set file containing hints: absolute/relative frame numbers.

There must be one line for each frame in a clip. Each line must contain two
numbers separated by the comma, optionally followed by - or +.
Numbers supplied on each line of file can not be out of [N-1,N+1] where N
is current frame number for absolute mode or out of [-1, 1] range
for relative mode. First number tells from which frame to pick up top
field and second number tells from which frame to pick up bottom field.

If optionally followed by + output frame will be marked as interlaced,
else if followed by - output frame will be marked as progressive, else
it will be marked same as input frame.
If line starts with # or ; that line is skipped.

Field matching filter for inverse telecine. It is meant to reconstruct the
progressive frames from a telecined stream. The filter does not drop duplicated
frames, so to achieve a complete inverse telecine fieldmatch needs to be
followed by a decimation filter such as decimate in the filtergraph.

The separation of the field matching and the decimation is notably motivated by
the possibility of inserting a de-interlacing filter fallback between the two.
If the source has mixed telecined and real interlaced content,
fieldmatch will not be able to match fields for the interlaced parts.
But these remaining combed frames will be marked as interlaced, and thus can be
de-interlaced by a later filter such as yadif before decimation.

In addition to the various configuration options, fieldmatch can take an
optional second stream, activated through the ppsrc option. If
enabled, the frames reconstruction will be based on the fields and frames from
this second stream. This allows the first input to be pre-processed in order to
help the various algorithms of the filter, while keeping the output lossless
(assuming the fields are matched properly). Typically, a field-aware denoiser,
or brightness/contrast adjustments can help.

Note that this filter uses the same algorithms as TIVTC/TFM (AviSynth project)
and VIVTC/VFM (VapourSynth project). The later is a light clone of TFM from
which fieldmatch is based on. While the semantic and usage are very
close, some behaviour and options names can differ.

The decimate filter currently only works for constant frame rate input.
If your input has mixed telecined (30fps) and progressive content with a lower
framerate like 24fps use the following filterchain to produce the necessary cfr
stream: dejudder,fps=30000/1001,fieldmatch,decimate.

The filter accepts the following options:

order

Specify the assumed field order of the input stream. Available values are:

‘auto’

Auto detect parity (use FFmpeg’s internal parity value).

‘bff’

Assume bottom field first.

‘tff’

Assume top field first.

Note that it is sometimes recommended not to trust the parity announced by the
stream.

Default value is auto.

mode

Set the matching mode or strategy to use. pc mode is the safest in the
sense that it won’t risk creating jerkiness due to duplicate frames when
possible, but if there are bad edits or blended fields it will end up
outputting combed frames when a good match might actually exist. On the other
hand, pcn_ub mode is the most risky in terms of creating jerkiness,
but will almost always find a good frame if there is one. The other values are
all somewhere in between pc and pcn_ub in terms of risking
jerkiness and creating duplicate frames versus finding good matches in sections
with bad edits, orphaned fields, blended fields, etc.

3-way matching, and trying 4th/5th matches if all 3 of the original matches are
detected as combed (p/c/n + u/b)

The parenthesis at the end indicate the matches that would be used for that
mode assuming order=tff (and field on auto or
top).

In terms of speed pc mode is by far the fastest and pcn_ub is
the slowest.

Default value is pc_n.

ppsrc

Mark the main input stream as a pre-processed input, and enable the secondary
input stream as the clean source to pick the fields from. See the filter
introduction for more details. It is similar to the clip2 feature from
VFM/TFM.

Default value is 0 (disabled).

field

Set the field to match from. It is recommended to set this to the same value as
order unless you experience matching failures with that setting. In
certain circumstances changing the field that is used to match from can have a
large impact on matching performance. Available values are:

‘auto’

Automatic (same value as order).

‘bottom’

Match from the bottom field.

‘top’

Match from the top field.

Default value is auto.

mchroma

Set whether or not chroma is included during the match comparisons. In most
cases it is recommended to leave this enabled. You should set this to 0
only if your clip has bad chroma problems such as heavy rainbowing or other
artifacts. Setting this to 0 could also be used to speed things up at
the cost of some accuracy.

Default value is 1.

y0

y1

These define an exclusion band which excludes the lines between y0 and
y1 from being included in the field matching decision. An exclusion
band can be used to ignore subtitles, a logo, or other things that may
interfere with the matching. y0 sets the starting scan line and
y1 sets the ending line; all lines in between y0 and
y1 (including y0 and y1) will be ignored. Setting
y0 and y1 to the same value will disable the feature.
y0 and y1 defaults to 0.

scthresh

Set the scene change detection threshold as a percentage of maximum change on
the luma plane. Good values are in the [8.0, 14.0] range. Scene change
detection is only relevant in case combmatch=sc. The range for
scthresh is [0.0, 100.0].

Default value is 12.0.

combmatch

When combatch is not none, fieldmatch will take into
account the combed scores of matches when deciding what match to use as the
final match. Available values are:

‘none’

No final matching based on combed scores.

‘sc’

Combed scores are only used when a scene change is detected.

‘full’

Use combed scores all the time.

Default is sc.

combdbg

Force fieldmatch to calculate the combed metrics for certain matches and
print them. This setting is known as micout in TFM/VFM vocabulary.
Available values are:

‘none’

No forced calculation.

‘pcn’

Force p/c/n calculations.

‘pcnub’

Force p/c/n/u/b calculations.

Default value is none.

cthresh

This is the area combing threshold used for combed frame detection. This
essentially controls how "strong" or "visible" combing must be to be detected.
Larger values mean combing must be more visible and smaller values mean combing
can be less visible or strong and still be detected. Valid settings are from
-1 (every pixel will be detected as combed) to 255 (no pixel will
be detected as combed). This is basically a pixel difference value. A good
range is [8, 12].

Default value is 9.

chroma

Sets whether or not chroma is considered in the combed frame decision. Only
disable this if your source has chroma problems (rainbowing, etc.) that are
causing problems for the combed frame detection with chroma enabled. Actually,
using chroma=0 is usually more reliable, except for the case
where there is chroma only combing in the source.

Default value is 0.

blockx

blocky

Respectively set the x-axis and y-axis size of the window used during combed
frame detection. This has to do with the size of the area in which
combpel pixels are required to be detected as combed for a frame to be
declared combed. See the combpel parameter description for more info.
Possible values are any number that is a power of 2 starting at 4 and going up
to 512.

Default value is 16.

combpel

The number of combed pixels inside any of the blocky by
blockx size blocks on the frame for the frame to be detected as
combed. While cthresh controls how "visible" the combing must be, this
setting controls "how much" combing there must be in any localized area (a
window defined by the blockx and blocky settings) on the
frame. Minimum value is 0 and maximum is blocky x blockx (at
which point no frames will ever be detected as combed). This setting is known
as MI in TFM/VFM vocabulary.

As a result of the field matching, we can see that some frames get duplicated.
To perform a complete inverse telecine, you need to rely on a decimation filter
after this operation. See for instance the decimate filter.

The same operation now matching from top fields (field=top)
looks like this:

The u and b matching are a bit special in the sense that they match
from the opposite parity flag. In the following examples, we assume that we are
currently matching the 2nd frame (Top:2, bottom:2). According to the match, a
’x’ is placed above and below each matched fields.

The output field order. Valid values are tff for top field first or bff
for bottom field first.

The default value is ‘tff’.

The transformation is done by shifting the picture content up or down
by one line, and filling the remaining line with appropriate picture content.
This method is consistent with most broadcast field order converters.

If the input video is not flagged as being interlaced, or it is already
flagged as being of the required output field order, then this filter does
not alter the incoming video.

It is very useful when converting to or from PAL DV material,
which is bottom field first.

Convert the video to specified constant frame rate by duplicating or dropping
frames as necessary.

It accepts the following parameters:

fps

The desired output frame rate. The default is 25.

round

Rounding method.

Possible values are:

zero

zero round towards 0

inf

round away from 0

down

round towards -infinity

up

round towards +infinity

near

round to nearest

The default is near.

start_time

Assume the first PTS should be the given value, in seconds. This allows for
padding/trimming at the start of stream. By default, no assumption is made
about the first frame’s expected PTS, so no padding or trimming is done.
For example, this could be set to 0 to pad the beginning with duplicates of
the first frame if a video stream starts after the audio stream or to trim any
frames with a negative PTS.

Alternatively, the options can be specified as a flat string:
fps[:round].

Pack two different video streams into a stereoscopic video, setting proper
metadata on supported codecs. The two views should have the same size and
framerate and processing will stop when the shorter video ends. Please note
that you may conveniently adjust view properties with the scale and
fps filters.

It accepts the following parameters:

format

The desired packing format. Supported values are:

sbs

The views are next to each other (default).

tab

The views are on top of each other.

lines

The views are packed by line.

columns

The views are packed by column.

frameseq

The views are temporally interleaved.

Some examples:

# Convert left and right views into a frame-sequential video
ffmpeg -i LEFT -i RIGHT -filter_complex framepack=frameseq OUTPUT
# Convert views into a side-by-side video with the same output resolution as the input
ffmpeg -i LEFT -i RIGHT -filter_complex [0:v]scale=w=iw/2[left],[1:v]scale=w=iw/2[right],[left][right]framepack=sbs OUTPUT

Change the frame rate by interpolating new video output frames from the source
frames.

This filter is not designed to function correctly with interlaced media. If
you wish to change the frame rate of interlaced media then you are required
to deinterlace before this filter and re-interlace after this filter.

A description of the accepted options follows.

fps

Specify the output frames per second. This option can also be specified
as a value alone. The default is 50.

interp_start

Specify the start of a range where the output frame will be created as a
linear interpolation of two frames. The range is [0-255],
the default is 15.

interp_end

Specify the end of a range where the output frame will be created as a
linear interpolation of two frames. The range is [0-255],
the default is 240.

scene

Specify the level at which a scene change is detected as a value between
0 and 100 to indicate a new scene; a low value reflects a low
probability for the current frame to introduce a new scene, while a higher
value means the current frame is more likely to be one.
The default is 7.

flags

Specify flags influencing the filter process.

Available value for flags is:

scene_change_detect, scd

Enable scene change detection using the value of the option scene.
This flag is enabled by default.

To enable the compilation of this filter, you need to install the frei0r
header and configure FFmpeg with --enable-frei0r.

It accepts the following parameters:

filter_name

The name of the frei0r effect to load. If the environment variable
FREI0R_PATH is defined, the frei0r effect is searched for in each of the
directories specified by the colon-separated list in FREIOR_PATH.
Otherwise, the standard frei0r paths are searched, in this order:
HOME/.frei0r-1/lib/, /usr/local/lib/frei0r-1/,
/usr/lib/frei0r-1/.

filter_params

A ’|’-separated list of parameters to pass to the frei0r effect.

A frei0r effect parameter can be a boolean (its value is either
"y" or "n"), a double, a color (specified as
R/G/B, where R, G, and B are floating point
numbers between 0.0 and 1.0, inclusive) or by a color description specified in the "Color"
section in the ffmpeg-utils manual), a position (specified as X/Y, where
X and Y are floating point numbers) and/or a string.

The number and types of parameters depend on the loaded effect. If an
effect parameter is not specified, the default value is set.

It splits (I)DCT into horizontal/vertical passes. Unlike the simple post-
processing filter, one of them is performed once per block, not per pixel.
This allows for much higher speed.

The filter accepts the following options:

quality

Set quality. This option defines the number of levels for averaging. It accepts
an integer in the range 4-5. Default value is 4.

qp

Force a constant quantization parameter. It accepts an integer in range 0-63.
If not set, the filter will use the QP from the video stream (if available).

strength

Set filter strength. It accepts an integer in range -15 to 32. Lower values mean
more details but also more artifacts, while higher values make the image smoother
but also blurrier. Default value is 0 − PSNR optimal.

use_bframe_qp

Enable the use of the QP from the B-Frames if set to 1. Using this
option may cause flicker since the B-Frames have often larger QP. Default is
0 (not enabled).

The colorspace is selected according to the specified options. If one
of the lum_expr, cb_expr, or cr_expr
options is specified, the filter will automatically select a YCbCr
colorspace. If one of the red_expr, green_expr, or
blue_expr options is specified, it will select an RGB
colorspace.

If one of the chrominance expression is not defined, it falls back on the other
one. If no alpha expression is specified it will evaluate to opaque value.
If none of chrominance expressions are specified, they will evaluate
to the luminance expression.

The expressions can use the following variables and functions:

N

The sequential number of the filtered frame, starting from 0.

X

Y

The coordinates of the current sample.

W

H

The width and height of the image.

SW

SH

Width and height scale depending on the currently filtered plane. It is the
ratio between the corresponding luma plane number of pixels and the current
plane ones. E.g. for YUV4:2:0 the values are 1,1 for the luma plane, and
0.5,0.5 for chroma planes.

T

Time of the current frame, expressed in seconds.

p(x, y)

Return the value of the pixel at location (x,y) of the current
plane.

lum(x, y)

Return the value of the pixel at location (x,y) of the luminance
plane.

cb(x, y)

Return the value of the pixel at location (x,y) of the
blue-difference chroma plane. Return 0 if there is no such plane.

cr(x, y)

Return the value of the pixel at location (x,y) of the
red-difference chroma plane. Return 0 if there is no such plane.

r(x, y)

g(x, y)

b(x, y)

Return the value of the pixel at location (x,y) of the
red/green/blue component. Return 0 if there is no such component.

alpha(x, y)

Return the value of the pixel at location (x,y) of the alpha
plane. Return 0 if there is no such plane.

For functions, if x and y are outside the area, the value will be
automatically clipped to the closer edge.

Fix the banding artifacts that are sometimes introduced into nearly flat
regions by truncation to 8-bit color depth.
Interpolate the gradients that should go where the bands are, and
dither them.

It is designed for playback only. Do not use it prior to
lossy compression, because compression tends to lose the dither and
bring back the bands.

It accepts the following parameters:

strength

The maximum amount by which the filter will change any one pixel. This is also
the threshold for detecting nearly flat regions. Acceptable values range from
.51 to 64; the default value is 1.2. Out-of-range values will be clipped to the
valid range.

radius

The neighborhood to fit the gradient to. A larger radius makes for smoother
gradients, but also prevents the filter from modifying the pixels near detailed
regions. Acceptable values are 8-32; the default value is 16. Out-of-range
values will be clipped to the valid range.

Alternatively, the options can be specified as a flat string:
strength[:radius]

A Hald CLUT is supposed to be a squared image of Level*Level*Level by
Level*Level*Level pixels. For a given Hald CLUT, FFmpeg will select the
biggest possible square starting at the top left of the picture. The remaining
padding pixels (bottom or right) will be ignored. This area can be used to add
a preview of the Hald CLUT.

Typically, the following generated Hald CLUT will be supported by the
haldclut filter:

This filter applies a global color histogram equalization on a
per-frame basis.

It can be used to correct video that has a compressed range of pixel
intensities. The filter redistributes the pixel intensities to
equalize their distribution across the intensity range. It may be
viewed as an "automatically adjusting contrast filter". This filter is
useful only for correcting degraded or poorly captured source
video.

The filter accepts the following options:

strength

Determine the amount of equalization to be applied. As the strength
is reduced, the distribution of pixel intensities more-and-more
approaches that of the input frame. The value must be a float number
in the range [0,1] and defaults to 0.200.

intensity

Set the maximum intensity that can generated and scale the output
values appropriately. The strength should be set as desired and then
the intensity can be limited if needed to avoid washing-out. The value
must be a float number in the range [0,1] and defaults to 0.210.

antibanding

Set the antibanding level. If enabled the filter will randomly vary
the luminance of output pixels by a small amount to avoid banding of
the histogram. Possible values are none, weak or
strong. It defaults to none.

The computed histogram is a representation of the color component
distribution in an image.

Standard histogram displays the color components distribution in an image.
Displays color graph for each color component. Shows distribution of
the Y, U, V, A or R, G, B components, depending on input format, in the
current frame. Below each graph a color component scale meter is shown.

The filter accepts the following options:

level_height

Set height of level. Default value is 200.
Allowed range is [50, 2048].

This filter tries to detect if the input frames are interlaced, progressive,
top or bottom field first. It will also try to detect fields that are
repeated between adjacent frames (a sign of telecine).

Single frame detection considers only immediately adjacent frames when classifying each frame.
Multiple frame detection incorporates the classification history of previous frames.

The filter will log these metadata values:

single.current_frame

Detected type of current frame using single-frame detection. One of:
“tff” (top field first), “bff” (bottom field first),
“progressive”, or “undetermined”

single.tff

Cumulative number of frames detected as top field first using single-frame detection.

multiple.tff

Cumulative number of frames detected as top field first using multiple-frame detection.

single.bff

Cumulative number of frames detected as bottom field first using single-frame detection.

multiple.current_frame

Detected type of current frame using multiple-frame detection. One of:
“tff” (top field first), “bff” (bottom field first),
“progressive”, or “undetermined”

multiple.bff

Cumulative number of frames detected as bottom field first using multiple-frame detection.

single.progressive

Cumulative number of frames detected as progressive using single-frame detection.

multiple.progressive

Cumulative number of frames detected as progressive using multiple-frame detection.

single.undetermined

Cumulative number of frames that could not be classified using single-frame detection.

multiple.undetermined

Cumulative number of frames that could not be classified using multiple-frame detection.

repeated.current_frame

Which field in the current frame is repeated from the last. One of “neither”, “top”, or “bottom”.

repeated.neither

Cumulative number of frames with no repeated field.

repeated.top

Cumulative number of frames with the top field repeated from the previous frame’s top field.

repeated.bottom

Cumulative number of frames with the bottom field repeated from the previous frame’s bottom field.

The filter accepts the following options:

intl_thres

Set interlacing threshold.

prog_thres

Set progressive threshold.

rep_thres

Threshold for repeated field detection.

half_life

Number of frames after which a given frame’s contribution to the
statistics is halved (i.e., it contributes only 0.5 to its
classification). The default of 0 means that all frames seen are given
full weight of 1.0 forever.

analyze_interlaced_flag

When this is not 0 then idet will use the specified number of frames to determine
if the interlaced flag is accurate, it will not count undetermined frames.
If the flag is found to be accurate it will be used without any further
computations, if it is found to be inaccurate it will be cleared without any
further computations. This allows inserting the idet filter as a low computational
method to clean up the interlaced flag

This filter allows one to process interlaced images fields without
deinterlacing them. Deinterleaving splits the input frame into 2
fields (so called half pictures). Odd lines are moved to the top
half of the output image, even lines to the bottom half.
You can process (filter) them independently and then re-interleave them.

Original Original New Frame
Frame 'j' Frame 'j+1' (tff)
========== =========== ==================
Line 0 --------------------> Frame 'j' Line 0
Line 1 Line 1 ----> Frame 'j+1' Line 1
Line 2 ---------------------> Frame 'j' Line 2
Line 3 Line 3 ----> Frame 'j+1' Line 3
... ... ...
New Frame + 1 will be generated by Frame 'j+2' and Frame 'j+3' and so on

It accepts the following optional parameters:

scan

This determines whether the interlaced frame is taken from the even
(tff - default) or odd (bff) lines of the progressive frame.

Set the threshold which affects the filter’s tolerance when
determining if a pixel line must be processed. It must be an integer
in the range [0,255] and defaults to 10. A value of 0 will result in
applying the process on every pixels.

map

Paint pixels exceeding the threshold value to white if set to 1.
Default is 0.

order

Set the fields order. Swap fields if set to 1, leave fields alone if
0. Default is 0.

This filter can be used to correct for radial distortion as can result from the use
of wide angle lenses, and thereby re-rectify the image. To find the right parameters
one can use tools available for example as part of opencv or simply trial-and-error.
To use opencv use the calibration sample (under samples/cpp) from the opencv sources
and extract the k1 and k2 coefficients from the resulting matrix.

Note that effectively the same filter is available in the open-source tools Krita and
Digikam from the KDE project.

In contrast to the vignette filter, which can also be used to compensate lens errors,
this filter corrects the distortion of the image, whereas vignette corrects the
brightness distribution, so you may want to use both filters together in certain
cases, though you will have to take care of ordering, i.e. whether vignetting should
be applied before or after lens correction.

The negated value for the pixel component value, clipped to the
minval-maxval range; it corresponds to the expression
"maxval-clipval+minval".

clip(val)

The computed value in val, clipped to the
minval-maxval range.

gammaval(gamma)

The computed gamma correction value of the pixel component value,
clipped to the minval-maxval range. It corresponds to the
expression
"pow((clipval-minval)/(maxval-minval)\,gamma)*(maxval-minval)+minval"

Merge the first input stream with the second input stream using per pixel
weights in the third input stream.

A value of 0 in the third stream pixel component means that pixel component
from first stream is returned unchanged, while maximum value (eg. 255 for
8-bit videos) means that pixel component from second stream is returned
unchanged. Intermediate values define the amount of merging between both
input stream’s pixel components.

This filter accepts the following options:

planes

Set which planes will be processed as bitmap, unprocessed planes will be
copied from first stream.
By default value 0xf, all planes will be processed.

The filter accepts up to 4 input streams, and merge selected input
planes to the output video.

This filter accepts the following options:

mapping

Set input to output plane mapping. Default is 0.

The mappings is specified as a bitmap. It should be specified as a
hexadecimal number in the form 0xAa[Bb[Cc[Dd]]]. ’Aa’ describes the
mapping for the first plane of the output stream. ’A’ sets the number of
the input stream to use (from 0 to 3), and ’a’ the plane number of the
corresponding input to use (from 0 to 3). The rest of the mappings is
similar, ’Bb’ describes the mapping for the output stream second
plane, ’Cc’ describes the mapping for the output stream third plane and
’Dd’ describes the mapping for the output stream fourth plane.

The algorithm to be used for motion estimation. Following values are accepted:

‘esa’

Exhaustive search algorithm.

‘tss’

Three step search algorithm.

‘tdls’

Two dimensional logarithmic search algorithm.

‘ntss’

New three step search algorithm.

‘fss’

Four step search algorithm.

‘ds’

Diamond search algorithm.

‘hexbs’

Hexagon-based search algorithm.

‘epzs’

Enhanced predictive zonal search algorithm.

‘umh’

Uneven multi-hexagon search algorithm.

Default algorithm is ‘epzs’.

‘mb_size’

Macroblock size. Default 16.

‘search_param’

Motion estimation search parameter. Default 32.

‘vsmbc’

Enable variable-size block motion compensation. Motion estimation is applied with smaller block sizes at object boundaries in order to make the them less blur. Default is 0 (disabled).

scd

Scene change detection method. Scene change leads motion vectors to be in random direction. Scene change detection replace interpolated frames by duplicate ones. May not be needed for other modes. Following values are accepted:

‘none’

Disable scene change detection.

‘fdiff’

Frame difference. Corresponding pixel values are compared and if it satisfies scd_threshold scene change is detected.

Drop frames that do not differ greatly from the previous frame in
order to reduce frame rate.

The main use of this filter is for very-low-bitrate encoding
(e.g. streaming over dialup modem), but it could in theory be used for
fixing movies that were inverse-telecined incorrectly.

A description of the accepted options follows.

max

Set the maximum number of consecutive frames which can be dropped (if
positive), or the minimum interval between dropped frames (if
negative). If the value is 0, the frame is dropped unregarding the
number of previous sequentially dropped frames.

Default value is 0.

hi

lo

frac

Set the dropping threshold values.

Values for hi and lo are for 8x8 pixel blocks and
represent actual pixel value differences, so a threshold of 64
corresponds to 1 unit of difference for each pixel, or the same spread
out differently over the block.

A frame is a candidate for dropping if no 8x8 blocks differ by more
than a threshold of hi, and if no more than frac blocks (1
meaning the whole image) differ by more than a threshold of lo.

Default value for hi is 64*12, default value for lo is
64*5, and default value for frac is 0.33.

Each pixel is adjusted by looking for other pixels with similar contexts. This
context similarity is defined by comparing their surrounding patches of size
pxp. Patches are searched in an area of rxr
around the pixel.

Note that the research area defines centers for patches, which means some
patches will be made of pixels outside that research area.

Mandatory option, without binary file filter can not work.
Currently file can be found here:
https://github.com/dubhater/vapoursynth-nnedi3/blob/master/src/nnedi3_weights.bin

deint

Set which frames to deinterlace, by default it is all.
Can be all or interlaced.

field

Set mode of operation.

Can be one of the following:

‘af’

Use frame flags, both fields.

‘a’

Use frame flags, single field.

‘t’

Use top field only.

‘b’

Use bottom field only.

‘tf’

Use both fields, top first.

‘bf’

Use both fields, bottom first.

planes

Set which planes to process, by default filter process all frames.

nsize

Set size of local neighborhood around each pixel, used by the predictor neural
network.

Can be one of the following:

‘s8x6’

‘s16x6’

‘s32x6’

‘s48x6’

‘s8x4’

‘s16x4’

‘s32x4’

nns

Set the number of neurons in predicctor neural network.
Can be one of the following:

‘n16’

‘n32’

‘n64’

‘n128’

‘n256’

qual

Controls the number of different neural network predictions that are blended
together to compute the final output value. Can be fast, default or
slow.

etype

Set which set of weights to use in the predictor.
Can be one of the following:

‘a’

weights trained to minimize absolute error

‘s’

weights trained to minimize squared error

pscrn

Controls whether or not the prescreener neural network is used to decide
which pixels should be processed by the predictor neural network and which
can be handled by simple cubic interpolation.
The prescreener is trained to know whether cubic interpolation will be
sufficient for a pixel or whether it should be predicted by the predictor nn.
The computational complexity of the prescreener nn is much less than that of
the predictor nn. Since most pixels can be handled by cubic interpolation,
using the prescreener generally results in much faster processing.
The prescreener is pretty accurate, so the difference between using it and not
using it is almost always unnoticeable.

Dilate an image by using a specific structuring element.
It corresponds to the libopencv function cvDilate.

It accepts the parameters: struct_el|nb_iterations.

struct_el represents a structuring element, and has the syntax:
colsxrows+anchor_xxanchor_y/shape

cols and rows represent the number of columns and rows of
the structuring element, anchor_x and anchor_y the anchor
point, and shape the shape for the structuring element. shape
must be "rect", "cross", "ellipse", or "custom".

If the value for shape is "custom", it must be followed by a
string of the form "=filename". The file with name
filename is assumed to represent a binary image, with each
printable character corresponding to a bright pixel. When a custom
shape is used, cols and rows are ignored, the number
or columns and rows of the read file are assumed instead.

The default value for struct_el is "3x3+0x0/rect".

nb_iterations specifies the number of times the transform is
applied to the image, and defaults to 1.

Some examples:

# Use the default values
ocv=dilate
# Dilate using a structuring element with a 5x5 cross, iterating two times
ocv=filter_name=dilate:filter_params=5x5+2x2/cross|2
# Read the shape from the file diamond.shape, iterating two times.
# The file diamond.shape may contain a pattern of characters like this
# *
# ***
# *****
# ***
# *
# The specified columns and rows are ignored
# but the anchor point coordinates are not
ocv=dilate:0x0+2x2/custom=diamond.shape|2

It takes two inputs and has one output. The first input is the "main"
video on which the second input is overlaid.

It accepts the following parameters:

A description of the accepted options follows.

x

y

Set the expression for the x and y coordinates of the overlaid video
on the main video. Default value is "0" for both expressions. In case
the expression is invalid, it is set to a huge value (meaning that the
overlay will not be displayed within the output visible area).

eof_action

The action to take when EOF is encountered on the secondary input; it accepts
one of the following values:

repeat

Repeat the last frame (the default).

endall

End both streams.

pass

Pass the main input through.

eval

Set when the expressions for x, and y are evaluated.

It accepts the following values:

‘init’

only evaluate expressions once during the filter initialization or
when a command is processed

‘frame’

evaluate expressions for each incoming frame

Default value is ‘frame’.

shortest

If set to 1, force the output to terminate when the shortest input
terminates. Default value is 0.

format

Set the format for the output video.

It accepts the following values:

‘yuv420’

force YUV420 output

‘yuv422’

force YUV422 output

‘yuv444’

force YUV444 output

‘rgb’

force RGB output

Default value is ‘yuv420’.

rgb (deprecated)

If set to 1, force the filter to accept inputs in the RGB
color space. Default value is 0. This option is deprecated, use
format instead.

repeatlast

If set to 1, force the filter to draw the last overlay frame over the
main input until the end of the stream. A value of 0 disables this
behavior. Default value is 1.

The x, and y expressions can contain the following
parameters.

main_w, W

main_h, H

The main input width and height.

overlay_w, w

overlay_h, h

The overlay input width and height.

x

y

The computed values for x and y. They are evaluated for
each new frame.

hsub

vsub

horizontal and vertical chroma subsample values of the output
format. For example for the pixel format "yuv422p" hsub is 2 and
vsub is 1.

n

the number of input frame, starting from 0

pos

the position in the file of the input frame, NAN if unknown

t

The timestamp, expressed in seconds. It’s NAN if the input timestamp is unknown.

Note that the n, pos, t variables are available only
when evaluation is done per frame, and will evaluate to NAN
when eval is set to ‘init’.

Be aware that frames are taken from each input video in timestamp
order, hence, if their initial timestamps differ, it is a good idea
to pass the two inputs through a setpts=PTS-STARTPTS filter to
have them begin in the same zero timestamp, as the example for
the movie filter does.

You can chain together more overlays but you should test the
efficiency of such approach.

Set the maximum number of colors to quantize in the palette.
Note: the palette will still contain 256 colors; the unused palette entries
will be black.

reserve_transparent

Create a palette of 255 colors maximum and reserve the last one for
transparency. Reserving the transparency color is useful for GIF optimization.
If not set, the maximum of colors in the palette will be 256. You probably want
to disable this option for a standalone image.
Set by default.

stats_mode

Set statistics mode.

It accepts the following values:

‘full’

Compute full frame histograms.

‘diff’

Compute histograms only for the part that differs from previous frame. This
might be relevant to give more importance to the moving part of your input if
the background is static.

‘single’

Compute new histogram for each frame.

Default value is full.

The filter also exports the frame metadata lavfi.color_quant_ratio
(nb_color_in / nb_color_out) which you can use to evaluate the degree of
color quantization of the palette. This information is also visible at
info logging level.

The filter takes two inputs: one video stream and a palette. The palette must
be a 256 pixels image.

It accepts the following options:

dither

Select dithering mode. Available algorithms are:

‘bayer’

Ordered 8x8 bayer dithering (deterministic)

‘heckbert’

Dithering as defined by Paul Heckbert in 1982 (simple error diffusion).
Note: this dithering is sometimes considered "wrong" and is included as a
reference.

‘floyd_steinberg’

Floyd and Steingberg dithering (error diffusion)

‘sierra2’

Frankie Sierra dithering v2 (error diffusion)

‘sierra2_4a’

Frankie Sierra dithering v2 "Lite" (error diffusion)

Default is sierra2_4a.

bayer_scale

When bayer dithering is selected, this option defines the scale of the
pattern (how much the crosshatch pattern is visible). A low value means more
visible pattern for less banding, and higher value means less visible pattern
at the cost of more banding.

The option must be an integer value in the range [0,5]. Default is 2.

diff_mode

If set, define the zone to process

‘rectangle’

Only the changing rectangle will be reprocessed. This is similar to GIF
cropping/offsetting compression mechanism. This option can be useful for speed
if only a part of the image is changing, and has use cases such as limiting the
scope of the error diffusal dither to the rectangle that bounds the
moving scene (it leads to more deterministic output if the scene doesn’t change
much, and as a result less moving noise and better GIF compression).

Correct perspective of video not recorded perpendicular to the screen.

A description of the accepted parameters follows.

x0

y0

x1

y1

x2

y2

x3

y3

Set coordinates expression for top left, top right, bottom left and bottom right corners.
Default values are 0:0:W:0:0:H:W:H with which perspective will remain unchanged.
If the sense option is set to source, then the specified points will be sent
to the corners of the destination. If the sense option is set to destination,
then the corners of the source will be sent to the specified coordinates.

The expressions can use the following variables:

W

H

the width and height of video frame.

in

Input frame count.

on

Output frame count.

interpolation

Set interpolation for perspective correction.

It accepts the following values:

‘linear’

‘cubic’

Default value is ‘linear’.

sense

Set interpretation of coordinate options.

It accepts the following values:

‘0, source’

Send point in the source specified by the given coordinates to
the corners of the destination.

‘1, destination’

Send the corners of the source to the point in the destination specified
by the given coordinates.

Default value is ‘source’.

eval

Set when the expressions for coordinates x0,y0,...x3,y3 are evaluated.

It accepts the following values:

‘init’

only evaluate expressions once during the filter initialization or
when a command is processed

Delay interlaced video by one field time so that the field order changes.

The intended use is to fix PAL movies that have been captured with the
opposite field order to the film-to-video transfer.

A description of the accepted parameters follows.

mode

Set phase mode.

It accepts the following values:

‘t’

Capture field order top-first, transfer bottom-first.
Filter will delay the bottom field.

‘b’

Capture field order bottom-first, transfer top-first.
Filter will delay the top field.

‘p’

Capture and transfer with the same field order. This mode only exists
for the documentation of the other options to refer to, but if you
actually select it, the filter will faithfully do nothing.

‘a’

Capture field order determined automatically by field flags, transfer
opposite.
Filter selects among ‘t’ and ‘b’ modes on a frame by frame
basis using field flags. If no field information is available,
then this works just like ‘u’.

‘u’

Capture unknown or varying, transfer opposite.
Filter selects among ‘t’ and ‘b’ on a frame by frame basis by
analyzing the images and selecting the alternative that produces best
match between the fields.

Capture determined by field flags, transfer unknown or varying.
Filter selects among ‘t’, ‘b’ and ‘p’ using field flags and
image analysis. If no field information is available, then this works just
like ‘U’. This is the default mode.

‘U’

Both capture and transfer unknown or varying.
Filter selects among ‘t’, ‘b’ and ‘p’ using image analysis only.

Enable the specified chain of postprocessing subfilters using libpostproc. This
library should be automatically selected with a GPL build (--enable-gpl).
Subfilters must be separated by ’/’ and can be disabled by prepending a ’-’.
Each subfilter and some options have a short and a long name that can be used
interchangeably, i.e. dr/dering are the same.

The filters accept the following options:

subfilters

Set postprocessing subfilters string.

All subfilters share common options to determine their scope:

a/autoq

Honor the quality commands for this subfilter.

c/chrom

Do chrominance filtering, too (default).

y/nochrom

Do luminance filtering only (no chrominance).

n/noluma

Do chrominance filtering only (no luminance).

These options can be appended after the subfilter name, separated by a ’|’.

Obtain the average, maximum and minimum PSNR (Peak Signal to Noise
Ratio) between two input videos.

This filter takes in input two input videos, the first input is
considered the "main" source and is passed unchanged to the
output. The second input is used as a "reference" video for computing
the PSNR.

Both video inputs must have the same resolution and pixel format for
this filter to work correctly. Also it assumes that both inputs
have the same number of frames, which are compared one by one.

The obtained average PSNR is printed through the logging system.

The filter stores the accumulated MSE (mean squared error) of each
frame, and at the end of the processing it is averaged across all frames
equally, and the following formula is applied to obtain the PSNR:

PSNR = 10*log10(MAX^2/MSE)

Where MAX is the average of the maximum values of each component of the
image.

The description of the accepted parameters follows.

stats_file, f

If specified the filter will use the named file to save the PSNR of
each individual frame. When filename equals "-" the data is sent to
standard output.

stats_version

Specifies which version of the stats file format to use. Details of
each format are written below.
Default value is 1.

stats_add_max

Determines whether the max value is output to the stats log.
Default value is 0.
Requires stats_version >= 2. If this is set and stats_version < 2,
the filter will return an error.

The file printed if stats_file is selected, contains a sequence of
key/value pairs of the form key:value for each compared
couple of frames.

If a stats_version greater than 1 is specified, a header line precedes
the list of per-frame-pair stats, with key value pairs following the frame
format with the following parameters:

psnr_log_version

The version of the log file format. Will match stats_version.

fields

A comma separated list of the per-frame-pair parameters included in
the log.

A description of each shown per-frame-pair parameter follows:

n

sequential number of the input frame, starting from 1

mse_avg

Mean Square Error pixel-by-pixel average difference of the compared
frames, averaged over all the image components.

mse_y, mse_u, mse_v, mse_r, mse_g, mse_g, mse_a

Mean Square Error pixel-by-pixel average difference of the compared
frames for the component specified by the suffix.

psnr_y, psnr_u, psnr_v, psnr_r, psnr_g, psnr_b, psnr_a

Peak Signal to Noise ratio of the compared frames for the component
specified by the suffix.

max_avg, max_y, max_u, max_v

Maximum allowed value for each channel, and average over all
channels.

The pullup filter is designed to take advantage of future context in making
its decisions. This filter is stateless in the sense that it does not lock
onto a pattern to follow, but it instead looks forward to the following
fields in order to identify matches and rebuild progressive frames.

To produce content with an even framerate, insert the fps filter after
pullup, use fps=24000/1001 if the input frame rate is 29.97fps,
fps=24 for 30fps and the (rare) telecined 25fps input.

The filter accepts the following options:

jl

jr

jt

jb

These options set the amount of "junk" to ignore at the left, right, top, and
bottom of the image, respectively. Left and right are in units of 8 pixels,
while top and bottom are in units of 2 lines.
The default is 8 pixels on each side.

sb

Set the strict breaks. Setting this option to 1 will reduce the chances of
filter generating an occasional mismatched frame, but it may also cause an
excessive number of frames to be dropped during high motion sequences.
Conversely, setting it to -1 will make filter match fields more easily.
This may help processing of video where there is slight blurring between
the fields, but may also cause there to be interlaced frames in the output.
Default value is 0.

mp

Set the metric plane to use. It accepts the following values:

‘l’

Use luma plane.

‘u’

Use chroma blue plane.

‘v’

Use chroma red plane.

This option may be set to use chroma plane instead of the default luma plane
for doing filter’s computations. This may improve accuracy on very clean
source material, but more likely will decrease accuracy, especially if there
is chroma noise (rainbow effect) or any grayscale video.
The main purpose of setting mp to a chroma plane is to reduce CPU
load and make pullup usable in realtime on slow machines.

For best results (without duplicated frames in the output file) it is
necessary to change the output frame rate. For example, to inverse
telecine NTSC input:

Flush video frames from internal cache of frames into a random order.
No frame is discarded.
Inspired by frei0r nervous filter.

frames

Set size in number of frames of internal cache, in range from 2 to
512. Default is 30.

seed

Set seed for random number generator, must be an integer included between
0 and UINT32_MAX. If not specified, or if explicitly set to
less than 0, the filter will try to use a good random seed on a
best effort basis.

Read vertical interval timecode (VITC) information from the top lines of a
video frame.

The filter adds frame metadata key lavfi.readvitc.tc_str with the
timecode value, if a valid timecode has been detected. Further metadata key
lavfi.readvitc.found is set to 0/1 depending on whether
timecode data has been found or not.

This filter accepts the following options:

scan_max

Set the maximum number of lines to scan for VITC data. If the value is set to
-1 the full video frame is scanned. Default is 45.

thr_b

Set the luma threshold for black. Accepts float numbers in the range [0.0,1.0],
default value is 0.2. The value must be equal or less than thr_w.

thr_w

Set the luma threshold for white. Accepts float numbers in the range [0.0,1.0],
default value is 0.6. The value must be equal or greater than thr_b.

Destination pixel at position (X, Y) will be picked from source (x, y) position
where x = Xmap(X, Y) and y = Ymap(X, Y). If mapping values are out of range, zero
value for pixel will be used for destination pixel.

Xmap and Ymap input video streams must be of same dimensions. Output video stream
will have Xmap/Ymap video stream dimensions.
Xmap and Ymap input video streams are 16bit depth, single channel.

Suppress a TV station logo, using an image file to determine which
pixels comprise the logo. It works by filling in the pixels that
comprise the logo with neighboring pixels.

The filter accepts the following options:

filename, f

Set the filter bitmap file, which can be any image format supported by
libavformat. The width and height of the image file must match those of the
video stream being processed.

Pixels in the provided bitmap image with a value of zero are not
considered part of the logo, non-zero pixels are considered part of
the logo. If you use white (255) for the logo and black (0) for the
rest, you will be safe. For making the filter bitmap, it is
recommended to take a screen capture of a black frame with the logo
visible, and then using a threshold filter followed by the erode
filter once or twice.

If needed, little splotches can be fixed manually. Remember that if
logo pixels are not covered, the filter quality will be much
reduced. Marking too many pixels as part of the logo does not hurt as
much, but it will increase the amount of blurring needed to cover over
the image and will destroy more information than necessary, and extra
pixels will slow things down on a large logo.

Set an expression for the angle by which to rotate the input video
clockwise, expressed as a number of radians. A negative value will
result in a counter-clockwise rotation. By default it is set to "0".

This expression is evaluated for each frame.

out_w, ow

Set the output width expression, default value is "iw".
This expression is evaluated just once during configuration.

out_h, oh

Set the output height expression, default value is "ih".
This expression is evaluated just once during configuration.

bilinear

Enable bilinear interpolation if set to 1, a value of 0 disables
it. Default value is 1.

fillcolor, c

Set the color used to fill the output area not covered by the rotated
image. For the general syntax of this option, check the "Color" section in the
ffmpeg-utils manual. If the special value "none" is selected then no
background is printed (useful for example if the background is never shown).

Default value is "black".

The expressions for the angle and the output size can contain the
following constants and functions:

n

sequential number of the input frame, starting from 0. It is always NAN
before the first frame is filtered.

t

time in seconds of the input frame, it is set to 0 when the filter is
configured. It is always NAN before the first frame is filtered.

hsub

vsub

horizontal and vertical chroma subsample values. For example for the
pixel format "yuv422p" hsub is 2 and vsub is 1.

in_w, iw

in_h, ih

the input video width and height

out_w, ow

out_h, oh

the output width and height, that is the size of the padded area as
specified by the width and height expressions

rotw(a)

roth(a)

the minimal width/height required for completely containing the input
video rotated by a radians.

These are only available when computing the out_w and
out_h expressions.

Set the output video dimension expression. Default value is the input
dimension.

If the value is 0, the input width is used for the output.

If one of the values is -1, the scale filter will use a value that
maintains the aspect ratio of the input image, calculated from the
other specified dimension. If both of them are -1, the input size is
used

If one of the values is -n with n > 1, the scale filter will also use a value
that maintains the aspect ratio of the input image, calculated from the other
specified dimension. After that it will, however, make sure that the calculated
dimension is divisible by n and adjust the value if necessary.

See below for the list of accepted constants for use in the dimension
expression.

eval

Specify when to evaluate width and height expression. It accepts the following values:

‘init’

Only evaluate expressions once during the filter initialization or when a command is processed.

‘frame’

Evaluate expressions for each incoming frame.

Default value is ‘init’.

interl

Set the interlacing mode. It accepts the following values:

‘1’

Force interlaced aware scaling.

‘0’

Do not apply interlaced scaling.

‘-1’

Select interlaced aware scaling depending on whether the source frames
are flagged as interlaced or not.

Set libswscale input parameters for scaling algorithms that need them. See
(ffmpeg-scaler)the ffmpeg-scaler manual for the
complete documentation. If not explicitly specified the filter applies
empty parameters.

Set color space conforming to the United States Federal Communications
Commission (FCC) Code of Federal Regulations (CFR) Title 47 (2003) 73.682 (a).

‘bt601’

Set color space conforming to:

ITU Radiocommunication Sector (ITU-R) Recommendation BT.601

ITU-R Rec. BT.470-6 (1998) Systems B, B1, and G

Society of Motion Picture and Television Engineers (SMPTE) ST 170:2004

‘smpte240m’

Set color space conforming to SMPTE ST 240:1999.

in_range

out_range

Set in/output YCbCr sample range.

This allows the autodetected value to be overridden as well as allows forcing
a specific value used for the output and encoder. If not specified, the
range depends on the pixel format. Possible values:

‘auto’

Choose automatically.

‘jpeg/full/pc’

Set full range (0-255 in case of 8-bit luma).

‘mpeg/tv’

Set "MPEG" range (16-235 in case of 8-bit luma).

force_original_aspect_ratio

Enable decreasing or increasing output video width or height if necessary to
keep the original aspect ratio. Possible values:

‘disable’

Scale the video as specified and disable this feature.

‘decrease’

The output video dimensions will automatically be decreased if needed.

‘increase’

The output video dimensions will automatically be increased if needed.

One useful instance of this option is that when you know a specific device’s
maximum allowed resolution, you can use this to limit the output video to
that, while retaining the aspect ratio. For example, device A allows
1280x720 playback, and your video is 1920x800. Using this option (set it to
decrease) and specifying 1280x720 to the command line makes the output
1280x533.

Please note that this is a different thing than specifying -1 for w
or h, you still need to specify the output resolution for this option
to work.

The values of the w and h options are expressions
containing the following constants:

in_w

in_h

The input width and height

iw

ih

These are the same as in_w and in_h.

out_w

out_h

The output (scaled) width and height

ow

oh

These are the same as out_w and out_h

a

The same as iw / ih

sar

input sample aspect ratio

dar

The input display aspect ratio. Calculated from (iw / ih) * sar.

hsub

vsub

horizontal and vertical input chroma subsample values. For example for the
pixel format "yuv422p" hsub is 2 and vsub is 1.

ohsub

ovsub

horizontal and vertical output chroma subsample values. For example for the
pixel format "yuv422p" hsub is 2 and vsub is 1.

Use the NVIDIA Performance Primitives (libnpp) to perform scaling and/or pixel
format conversion on CUDA video frames. Setting the output width and height
works in the same way as for the scale filter.

The following additional options are accepted:

format

The pixel format of the output CUDA frames. If set to the string "same" (the
default), the input format will be kept. Note that automatic format negotiation
and conversion is not yet supported for hardware frames

Adjust cyan, magenta, yellow and black (CMYK) to certain ranges of colors (such
as "reds", "yellows", "greens", "cyans", ...). The adjustment range is defined
by the "purity" of the color (that is, how saturated it already is).

All the adjustment settings (reds, yellows, ...) accept up to
4 space separated floating point adjustment values in the [-1,1] range,
respectively to adjust the amount of cyan, magenta, yellow and black for the
pixels of its range.

The setdar filter sets the Display Aspect Ratio for the filter
output video.

This is done by changing the specified Sample (aka Pixel) Aspect
Ratio, according to the following equation:

DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR

Keep in mind that the setdar filter does not modify the pixel
dimensions of the video frame. Also, the display aspect ratio set by
this filter may be changed by later filters in the filterchain,
e.g. in case of scaling or if another "setdar" or a "setsar" filter is
applied.

Note that as a consequence of the application of this filter, the
output display aspect ratio will change according to the equation
above.

Keep in mind that the sample aspect ratio set by the setsar
filter may be changed by later filters in the filterchain, e.g. if
another "setsar" or a "setdar" filter is applied.

It accepts the following parameters:

r, ratio, dar (setdar only), sar (setsar only)

Set the aspect ratio used by the filter.

The parameter can be a floating point number string, an expression, or
a string of the form num:den, where num and
den are the numerator and denominator of the aspect ratio. If
the parameter is not specified, it is assumed the value "0".
In case the form "num:den" is used, the : character
should be escaped.

max

Set the maximum integer value to use for expressing numerator and
denominator when reducing the expressed aspect ratio to a rational.
Default value is 100.

The parameter sar is an expression containing
the following constants:

E, PI, PHI

These are approximated values for the mathematical constants e
(Euler’s number), pi (Greek pi), and phi (the golden ratio).

w, h

The input width and height.

a

These are the same as w / h.

sar

The input sample aspect ratio.

dar

The input display aspect ratio. It is the same as
(w / h) * sar.

hsub, vsub

Horizontal and vertical chroma subsample values. For example, for the
pixel format "yuv422p" hsub is 2 and vsub is 1.

The setfield filter marks the interlace type field for the
output frames. It does not change the input frame, but only sets the
corresponding property, which affects how the frame is treated by
following filters (e.g. fieldorder or yadif).

The type of interlaced mode ("P" for "progressive", "T" for top field first, "B"
for bottom field first).

iskey

This is 1 if the frame is a key frame, 0 otherwise.

type

The picture type of the input frame ("I" for an I-frame, "P" for a
P-frame, "B" for a B-frame, or "?" for an unknown type).
Also refer to the documentation of the AVPictureType enum and of
the av_get_picture_type_char function defined in
libavutil/avutil.h.

checksum

The Adler-32 checksum (printed in hexadecimal) of all the planes of the input frame.

plane_checksum

The Adler-32 checksum (printed in hexadecimal) of each plane of the input frame,
expressed in the form "[c0c1c2c3]".

Evaluate various visual metrics that assist in determining issues associated
with the digitization of analog video media.

By default the filter will log these metadata values:

YMIN

Display the minimal Y value contained within the input frame. Expressed in
range of [0-255].

YLOW

Display the Y value at the 10% percentile within the input frame. Expressed in
range of [0-255].

YAVG

Display the average Y value within the input frame. Expressed in range of
[0-255].

YHIGH

Display the Y value at the 90% percentile within the input frame. Expressed in
range of [0-255].

YMAX

Display the maximum Y value contained within the input frame. Expressed in
range of [0-255].

UMIN

Display the minimal U value contained within the input frame. Expressed in
range of [0-255].

ULOW

Display the U value at the 10% percentile within the input frame. Expressed in
range of [0-255].

UAVG

Display the average U value within the input frame. Expressed in range of
[0-255].

UHIGH

Display the U value at the 90% percentile within the input frame. Expressed in
range of [0-255].

UMAX

Display the maximum U value contained within the input frame. Expressed in
range of [0-255].

VMIN

Display the minimal V value contained within the input frame. Expressed in
range of [0-255].

VLOW

Display the V value at the 10% percentile within the input frame. Expressed in
range of [0-255].

VAVG

Display the average V value within the input frame. Expressed in range of
[0-255].

VHIGH

Display the V value at the 90% percentile within the input frame. Expressed in
range of [0-255].

VMAX

Display the maximum V value contained within the input frame. Expressed in
range of [0-255].

SATMIN

Display the minimal saturation value contained within the input frame.
Expressed in range of [0-~181.02].

SATLOW

Display the saturation value at the 10% percentile within the input frame.
Expressed in range of [0-~181.02].

SATAVG

Display the average saturation value within the input frame. Expressed in range
of [0-~181.02].

SATHIGH

Display the saturation value at the 90% percentile within the input frame.
Expressed in range of [0-~181.02].

SATMAX

Display the maximum saturation value contained within the input frame.
Expressed in range of [0-~181.02].

HUEMED

Display the median value for hue within the input frame. Expressed in range of
[0-360].

HUEAVG

Display the average value for hue within the input frame. Expressed in range of
[0-360].

YDIF

Display the average of sample value difference between all values of the Y
plane in the current frame and corresponding values of the previous input frame.
Expressed in range of [0-255].

UDIF

Display the average of sample value difference between all values of the U
plane in the current frame and corresponding values of the previous input frame.
Expressed in range of [0-255].

VDIF

Display the average of sample value difference between all values of the V
plane in the current frame and corresponding values of the previous input frame.
Expressed in range of [0-255].

YBITDEPTH

Display bit depth of Y plane in current frame.
Expressed in range of [0-16].

UBITDEPTH

Display bit depth of U plane in current frame.
Expressed in range of [0-16].

VBITDEPTH

Display bit depth of V plane in current frame.
Expressed in range of [0-16].

The filter accepts the following options:

stat

out

stat specify an additional form of image analysis.
out output video with the specified type of pixel highlighted.

Both options accept the following values:

‘tout’

Identify temporal outliers pixels. A temporal outlier is a pixel
unlike the neighboring pixels of the same field. Examples of temporal outliers
include the results of video dropouts, head clogs, or tape tracking issues.

‘vrep’

Identify vertical line repetition. Vertical line repetition includes
similar rows of pixels within a frame. In born-digital video vertical line
repetition is common, but this pattern is uncommon in video digitized from an
analog source. When it occurs in video that results from the digitization of an
analog source it can indicate concealment from a dropout compensator.

‘brng’

Identify pixels that fall outside of legal broadcast range.

color, c

Set the highlight color for the out option. The default color is
yellow.

Set the luma radius. The option value must be a float number in
the range [0.1,5.0] that specifies the variance of the gaussian filter
used to blur the image (slower if larger). Default value is 1.0.

luma_strength, ls

Set the luma strength. The option value must be a float number
in the range [-1.0,1.0] that configures the blurring. A value included
in [0.0,1.0] will blur the image whereas a value included in
[-1.0,0.0] will sharpen the image. Default value is 1.0.

luma_threshold, lt

Set the luma threshold used as a coefficient to determine
whether a pixel should be blurred or not. The option value must be an
integer in the range [-30,30]. A value of 0 will filter all the image,
a value included in [0,30] will filter flat areas and a value included
in [-30,0] will filter edges. Default value is 0.

chroma_radius, cr

Set the chroma radius. The option value must be a float number in
the range [0.1,5.0] that specifies the variance of the gaussian filter
used to blur the image (slower if larger). Default value is 1.0.

chroma_strength, cs

Set the chroma strength. The option value must be a float number
in the range [-1.0,1.0] that configures the blurring. A value included
in [0.0,1.0] will blur the image whereas a value included in
[-1.0,0.0] will sharpen the image. Default value is 1.0.

chroma_threshold, ct

Set the chroma threshold used as a coefficient to determine
whether a pixel should be blurred or not. The option value must be an
integer in the range [-30,30]. A value of 0 will filter all the image,
a value included in [0,30] will filter flat areas and a value included
in [-30,0] will filter edges. Default value is 0.

If a chroma option is not explicitly set, the corresponding luma value
is set.

Obtain the SSIM (Structural SImilarity Metric) between two input videos.

This filter takes in input two input videos, the first input is
considered the "main" source and is passed unchanged to the
output. The second input is used as a "reference" video for computing
the SSIM.

Both video inputs must have the same resolution and pixel format for
this filter to work correctly. Also it assumes that both inputs
have the same number of frames, which are compared one by one.

The filter stores the calculated SSIM of each frame.

The description of the accepted parameters follows.

stats_file, f

If specified the filter will use the named file to save the SSIM of
each individual frame. When filename equals "-" the data is sent to
standard output.

The file printed if stats_file is selected, contains a sequence of
key/value pairs of the form key:value for each compared
couple of frames.

A description of each shown parameter follows:

n

sequential number of the input frame, starting from 1

Y, U, V, R, G, B

SSIM of the compared frames for the component specified by the suffix.

Apply a simple postprocessing filter that compresses and decompresses the image
at several (or - in the case of quality level 6 - all) shifts
and average the results.

The filter accepts the following options:

quality

Set quality. This option defines the number of levels for averaging. It accepts
an integer in the range 0-6. If set to 0, the filter will have no
effect. A value of 6 means the higher quality. For each increment of
that value the speed drops by a factor of approximately 2. Default value is
3.

qp

Force a constant quantization parameter. If not set, the filter will use the QP
from the video stream (if available).

To enable compilation of this filter you need to configure FFmpeg with
--enable-libass. This filter also requires a build with libavcodec and
libavformat to convert the passed subtitles file to ASS (Advanced Substation
Alpha) subtitles format.

The filter accepts the following options:

filename, f

Set the filename of the subtitle file to read. It must be specified.

original_size

Specify the size of the original video, the video for which the ASS file
was composed. For the syntax of this option, check the
(ffmpeg-utils)"Video size" section in the ffmpeg-utils manual.
Due to a misdesign in ASS aspect ratio arithmetic, this is necessary to
correctly scale the fonts if the aspect ratio has been changed.

fontsdir

Set a directory path containing fonts that can be used by the filter.
These fonts will be used in addition to whatever the font provider uses.

charenc

Set subtitles input character encoding. subtitles filter only. Only
useful if not UTF-8.

Double frame rate with unchanged height. Frames are inserted each
containing the second temporal field from the previous input frame and
the first temporal field from the next input frame. This mode relies on
the top_field_first flag. Useful for interlaced video displays with no
field synchronisation.

Note that the first two sets of the start/end options and the duration
option look at the frame timestamp, while the _frame variants simply count the
frames that pass through the filter. Also note that this filter does not modify
the timestamps. If you wish for the output timestamps to start at zero, insert a
setpts filter after the trim filter.

If multiple start or end options are set, this filter tries to be greedy and
keep all the frames that match at least one of the specified constraints. To keep
only the part that matches all the constraints at once, chain multiple trim
filters.

The defaults are such that all the input is kept. So it is possible to set e.g.
just the end values to keep everything before the specified time.

Apply ultra slow/simple postprocessing filter that compresses and decompresses
the image at several (or - in the case of quality level 8 - all)
shifts and average the results.

The way this differs from the behavior of spp is that uspp actually encodes &
decodes each case with libavcodec Snow, whereas spp uses a simplified intra only 8x8
DCT similar to MJPEG.

The filter accepts the following options:

quality

Set quality. This option defines the number of levels for averaging. It accepts
an integer in the range 0-8. If set to 0, the filter will have no
effect. A value of 8 means the higher quality. For each increment of
that value the speed drops by a factor of approximately 2. Default value is
3.

qp

Force a constant quantization parameter. If not set, the filter will use the QP
from the video stream (if available).

It transforms each frame from the video input into the wavelet domain,
using Cohen-Daubechies-Feauveau 9/7. Then it applies some filtering to
the obtained coefficients. It does an inverse wavelet transform after.
Due to wavelet properties, it should give a nice smoothed result, and
reduced noise, without blurring picture features.

This filter accepts the following options:

threshold

The filtering strength. The higher, the more filtered the video will be.
Hard thresholding can use a higher threshold than soft thresholding
before the video looks overfiltered.

method

The filtering method the filter will use.

It accepts the following values:

‘hard’

All values under the threshold will be zeroed.

‘soft’

All values under the threshold will be zeroed. All values above will be
reduced by the threshold.

Display 2 color component values in the two dimensional graph (which is called
a vectorscope).

This filter accepts the following options:

mode, m

Set vectorscope mode.

It accepts the following values:

‘gray’

Gray values are displayed on graph, higher brightness means more pixels have
same component color value on location in graph. This is the default mode.

‘color’

Gray values are displayed on graph. Surrounding pixels values which are not
present in video frame are drawn in gradient of 2 color components which are
set by option x and y. The 3rd color component is static.

Similar as color2 but higher frequency of same values x and y
on graph increases value of another color component, which is luminance by
default values of x and y.

‘color4’

Actual colors present in video frame are displayed on graph. If two different
colors map to same position on graph then color with higher value of component
not present in graph is picked.

‘color5’

Gray values are displayed on graph. Similar to color but with 3rd color
component picked from radial gradient.

x

Set which color component will be represented on X-axis. Default is 1.

y

Set which color component will be represented on Y-axis. Default is 2.

intensity, i

Set intensity, used by modes: gray, color, color3 and color5 for increasing brightness
of color component which represents frequency of (X, Y) location in graph.

envelope, e

‘none’

No envelope, this is default.

‘instant’

Instant envelope, even darkest single pixel will be clearly highlighted.

‘peak’

Hold maximum and minimum values presented in graph over time. This way you
can still spot out of range values without constantly looking at vectorscope.

‘peak+instant’

Peak and instant envelope combined together.

graticule, g

Set what kind of graticule to draw.

‘none’

‘green’

‘color’

opacity, o

Set graticule opacity.

flags, f

Set graticule flags.

‘white’

Draw graticule for white point.

‘black’

Draw graticule for black point.

‘name’

Draw color points short names.

bgopacity, b

Set background opacity.

lthreshold, l

Set low threshold for color component not represented on X or Y axis.
Values lower than this value will be ignored. Default is 0.
Note this value is multiplied with actual max possible value one pixel component
can have. So for 8-bit input and low threshold value of 0.1 actual threshold
is 0.1 * 255 = 25.

hthreshold, h

Set high threshold for color component not represented on X or Y axis.
Values higher than this value will be ignored. Default is 1.
Note this value is multiplied with actual max possible value one pixel component
can have. So for 8-bit input and high threshold value of 0.9 actual threshold
is 0.9 * 255 = 230.

This filter generates a file with relative translation and rotation
transform information about subsequent frames, which is then used by
the vidstabtransform filter.

To enable compilation of this filter you need to configure FFmpeg with
--enable-libvidstab.

This filter accepts the following options:

result

Set the path to the file used to write the transforms information.
Default value is transforms.trf.

shakiness

Set how shaky the video is and how quick the camera is. It accepts an
integer in the range 1-10, a value of 1 means little shakiness, a
value of 10 means strong shakiness. Default value is 5.

accuracy

Set the accuracy of the detection process. It must be a value in the
range 1-15. A value of 1 means low accuracy, a value of 15 means high
accuracy. Default value is 15.

stepsize

Set stepsize of the search process. The region around minimum is
scanned with 1 pixel resolution. Default value is 6.

mincontrast

Set minimum contrast. Below this value a local measurement field is
discarded. Must be a floating point value in the range 0-1. Default
value is 0.3.

tripod

Set reference frame number for tripod mode.

If enabled, the motion of the frames is compared to a reference frame
in the filtered stream, identified by the specified number. The idea
is to compensate all movements in a more-or-less static scene and keep
the camera view absolutely still.

If set to 0, it is disabled. The frames are counted starting from 1.

show

Show fields and transforms in the resulting frames. It accepts an
integer in the range 0-2. Default value is 0, which disables any
visualization.

Set path to the file used to read the transforms. Default value is
transforms.trf.

smoothing

Set the number of frames (value*2 + 1) used for lowpass filtering the
camera movements. Default value is 10.

For example a number of 10 means that 21 frames are used (10 in the
past and 10 in the future) to smoothen the motion in the video. A
larger value leads to a smoother video, but limits the acceleration of
the camera (pan/tilt movements). 0 is a special case where a static
camera is simulated.

optalgo

Set the camera path optimization algorithm.

Accepted values are:

‘gauss’

gaussian kernel low-pass filter on camera motion (default)

‘avg’

averaging on transformations

maxshift

Set maximal number of pixels to translate frames. Default value is -1,
meaning no limit.

maxangle

Set maximal angle in radians (degree*PI/180) to rotate frames. Default
value is -1, meaning no limit.

crop

Specify how to deal with borders that may be visible due to movement
compensation.

Available values are:

‘keep’

keep image information from previous frame (default)

‘black’

fill the border black

invert

Invert transforms if set to 1. Default value is 0.

relative

Consider transforms as relative to previous frame if set to 1,
absolute if set to 0. Default value is 0.

zoom

Set percentage to zoom. A positive value will result in a zoom-in
effect, a negative value in a zoom-out effect. Default value is 0 (no
zoom).

optzoom

Set optimal zooming to avoid borders.

Accepted values are:

‘0’

disabled

‘1’

optimal static zoom value is determined (only very strong movements
will lead to visible borders) (default)

‘2’

optimal adaptive zoom value is determined (no borders will be
visible), see zoomspeed

Note that the value given at zoom is added to the one calculated here.

zoomspeed

Set percent to zoom maximally each frame (enabled when
optzoom is set to 2). Range is from 0 to 5, default value is
0.25.

interpol

Specify type of interpolation.

Available values are:

‘no’

no interpolation

‘linear’

linear only horizontal

‘bilinear’

linear in both directions (default)

‘bicubic’

cubic in both directions (slow)

tripod

Enable virtual tripod mode if set to 1, which is equivalent to
relative=0:smoothing=0. Default value is 0.

Set center coordinates expressions. Respectively "w/2" and "h/2"
by default.

mode

Set forward/backward mode.

Available modes are:

‘forward’

The larger the distance from the central point, the darker the image becomes.

‘backward’

The larger the distance from the central point, the brighter the image becomes.
This can be used to reverse a vignette effect, though there is no automatic
detection to extract the lens angle and other settings (yet). It can
also be used to create a burning effect.

Default value is ‘forward’.

eval

Set evaluation mode for the expressions (angle, x0, y0).

It accepts the following values:

‘init’

Evaluate expressions only once during the filter initialization.

‘frame’

Evaluate expressions for each incoming frame. This is way slower than the
‘init’ mode since it requires all the scalers to be re-computed, but it
allows advanced dynamic expressions.

Default value is ‘init’.

dither

Set dithering to reduce the circular banding effects. Default is 1
(enabled).

aspect

Set vignette aspect. This setting allows one to adjust the shape of the vignette.
Setting this value to the SAR of the input will make a rectangular vignetting
following the dimensions of the video.

Based on the process described by Martin Weston for BBC R&D, and
implemented based on the de-interlace algorithm written by Jim
Easterbrook for BBC R&D, the Weston 3 field deinterlacing filter
uses filter coefficients calculated by BBC R&D.

There are two sets of filter coefficients, so called "simple":
and "complex". Which set of filter coefficients is used can
be set by passing an optional parameter:

filter

Set the interlacing filter coefficients. Accepts one of the following values:

‘simple’

Simple filter coefficient set.

‘complex’

More-complex filter coefficient set.

Default value is ‘complex’.

deint

Specify which frames to deinterlace. Accept one of the following values:

The waveform monitor plots color component intensity. By default luminance
only. Each column of the waveform corresponds to a column of pixels in the
source video.

It accepts the following options:

mode, m

Can be either row, or column. Default is column.
In row mode, the graph on the left side represents color component value 0 and
the right side represents value = 255. In column mode, the top side represents
color component value = 0 and bottom side represents value = 255.

intensity, i

Set intensity. Smaller values are useful to find out how many values of the same
luminance are distributed across input rows/columns.
Default value is 0.04. Allowed range is [0, 1].

mirror, r

Set mirroring mode. 0 means unmirrored, 1 means mirrored.
In mirrored mode, higher values will be represented on the left
side for row mode and at the top for column mode. Default is
1 (mirrored).

display, d

Set display mode.
It accepts the following values:

‘overlay’

Presents information identical to that in the parade, except
that the graphs representing color components are superimposed directly
over one another.

This display mode makes it easier to spot relative differences or similarities
in overlapping areas of the color components that are supposed to be identical,
such as neutral whites, grays, or blacks.

‘stack’

Display separate graph for the color components side by side in
row mode or one below the other in column mode.

‘parade’

Display separate graph for the color components side by side in
column mode or one below the other in row mode.

Using this display mode makes it easy to spot color casts in the highlights
and shadows of an image, by comparing the contours of the top and the bottom
graphs of each waveform. Since whites, grays, and blacks are characterized
by exactly equal amounts of red, green, and blue, neutral areas of the picture
should display three waveforms of roughly equal width/height. If not, the
correction is easy to perform by making level adjustments the three waveforms.

Default is stack.

components, c

Set which color components to display. Default is 1, which means only luminance
or red color component if input is in RGB colorspace. If is set for example to
7 it will display all 3 (if) available color components.

envelope, e

‘none’

No envelope, this is default.

‘instant’

Instant envelope, minimum and maximum values presented in graph will be easily
visible even with small step value.

‘peak’

Hold minimum and maximum values presented in graph across time. This way you
can still spot out of range values without constantly looking at waveforms.

Set the output video dimension expression. Default value is the input
dimension.

If the width or w is 0, the input width is used for the output.
If the height or h is 0, the input height is used for the output.

If one of the values is -1, the zscale filter will use a value that
maintains the aspect ratio of the input image, calculated from the
other specified dimension. If both of them are -1, the input size is
used

If one of the values is -n with n > 1, the zscale filter will also use a value
that maintains the aspect ratio of the input image, calculated from the other
specified dimension. After that it will, however, make sure that the calculated
dimension is divisible by n and adjust the value if necessary.

See below for the list of accepted constants for use in the dimension
expression.

A string representing the pixel format of the buffered video frames.
It may be a number corresponding to a pixel format, or a pixel format
name.

time_base

Specify the timebase assumed by the timestamps of the buffered frames.

frame_rate

Specify the frame rate expected for the video stream.

pixel_aspect, sar

The sample (pixel) aspect ratio of the input video.

sws_param

Specify the optional parameters to be used for the scale filter which
is automatically inserted when an input change is detected in the
input size or format.

hw_frames_ctx

When using a hardware pixel format, this should be a reference to an
AVHWFramesContext describing input frames.

For example:

buffer=width=320:height=240:pix_fmt=yuv410p:time_base=1/24:sar=1

will instruct the source to accept video frames with size 320x240 and
with format "yuv410p", assuming 1/24 as the timestamps timebase and
square pixels (1:1 sample aspect ratio).
Since the pixel format with name "yuv410p" corresponds to the number 6
(check the enum AVPixelFormat definition in libavutil/pixfmt.h),
this example corresponds to:

buffer=size=320x240:pixfmt=6:time_base=1/24:pixel_aspect=1/1

Alternatively, the options can be specified as a flat string, but this
syntax is deprecated:

The initial state of the cellular automaton can be defined through the
filename and pattern options. If such options are
not specified an initial state is created randomly.

At each new frame a new row in the video is filled with the result of
the cellular automaton next generation. The behavior when the whole
frame is filled is defined by the scroll option.

This source accepts the following options:

filename, f

Read the initial cellular automaton state, i.e. the starting row, from
the specified file.
In the file, each non-whitespace character is considered an alive
cell, a newline will terminate the row, and further characters in the
file will be ignored.

Each non-whitespace character in the string is considered an alive
cell, a newline will terminate the row, and further characters in the
string will be ignored.

rate, r

Set the video rate, that is the number of frames generated per second.
Default is 25.

random_fill_ratio, ratio

Set the random fill ratio for the initial cellular automaton row. It
is a floating point number value ranging from 0 to 1, defaults to
1/PHI.

This option is ignored when a file or a pattern is specified.

random_seed, seed

Set the seed for filling randomly the initial row, must be an integer
included between 0 and UINT32_MAX. If not specified, or if explicitly
set to -1, the filter will try to use a good random seed on a best
effort basis.

rule

Set the cellular automaton rule, it is a number ranging from 0 to 255.
Default value is 110.

If filename or pattern is specified, the size is set
by default to the width of the specified initial state row, and the
height is set to width * PHI.

If size is set, it must contain the width of the specified
pattern string, and the specified pattern will be centered in the
larger row.

If a filename or a pattern string is not specified, the size value
defaults to "320x518" (used for a randomly generated initial state).

scroll

If set to 1, scroll the output upward when all the rows in the output
have been already filled. If set to 0, the new generated row will be
written over the top row just after the bottom row is filled.
Defaults to 1.

start_full, full

If set to 1, completely fill the output with generated rows before
outputting the first frame.
This is the default behavior, for disabling set the value to 0.

stitch

If set to 1, stitch the left and right row edges together.
This is the default behavior, for disabling set the value to 0.

Specify the frame rate of the sourced video, as the number of frames
generated per second. It has to be a string in the format
frame_rate_num/frame_rate_den, an integer number, a floating point
number or a valid video frame rate abbreviation. The default value is
"25".

If not specified, or the expressed duration is negative, the video is
supposed to be generated forever.

Additionally, all options of the coreimage video filter are accepted.
A complete filterchain can be used for further processing of the
generated input without CPU-HOST transfer. See coreimage documentation
and examples for details.

Generate various test patterns, as generated by the MPlayer test filter.

The size of the generated video is fixed, and is 256x256.
This source is useful in particular for testing encoding features.

This source accepts the following options:

rate, r

Specify the frame rate of the sourced video, as the number of frames
generated per second. It has to be a string in the format
frame_rate_num/frame_rate_den, an integer number, a floating point
number or a valid video frame rate abbreviation. The default value is
"25".

The sourced input represents a life grid, each pixel represents a cell
which can be in one of two possible states, alive or dead. Every cell
interacts with its eight neighbours, which are the cells that are
horizontally, vertically, or diagonally adjacent.

At each interaction the grid evolves according to the adopted rule,
which specifies the number of neighbor alive cells which will make a
cell stay alive or born. The rule option allows one to specify
the rule to adopt.

This source accepts the following options:

filename, f

Set the file from which to read the initial grid state. In the file,
each non-whitespace character is considered an alive cell, and newline
is used to delimit the end of each row.

If this option is not specified, the initial grid is generated
randomly.

rate, r

Set the video rate, that is the number of frames generated per second.
Default is 25.

random_fill_ratio, ratio

Set the random fill ratio for the initial random grid. It is a
floating point number value ranging from 0 to 1, defaults to 1/PHI.
It is ignored when a file is specified.

random_seed, seed

Set the seed for filling the initial random grid, must be an integer
included between 0 and UINT32_MAX. If not specified, or if explicitly
set to -1, the filter will try to use a good random seed on a best
effort basis.

rule

Set the life rule.

A rule can be specified with a code of the kind "SNS/BNB",
where NS and NB are sequences of numbers in the range 0-8,
NS specifies the number of alive neighbor cells which make a
live cell stay alive, and NB the number of alive neighbor cells
which make a dead cell to become alive (i.e. to "born").
"s" and "b" can be used in place of "S" and "B", respectively.

Alternatively a rule can be specified by an 18-bits integer. The 9
high order bits are used to encode the next cell state if it is alive
for each number of neighbor alive cells, the low order bits specify
the rule for "borning" new cells. Higher order bits encode for an
higher number of neighbor cells.
For example the number 6153 = (12<<9)+9 specifies a stay alive
rule of 12 and a born rule of 9, which corresponds to "S23/B03".

Default value is "S23/B3", which is the original Conway’s game of life
rule, and will keep a cell alive if it has 2 or 3 neighbor alive
cells, and will born a new cell if there are three alive cells around
a dead cell.

If filename is specified, the size is set by default to the
same size of the input file. If size is set, it must contain
the size specified in the input file, and the initial grid defined in
that file is centered in the larger resulting area.

If a filename is not specified, the size value defaults to "320x240"
(used for a randomly generated initial grid).

stitch

If set to 1, stitch the left and right grid edges together, and the
top and bottom edges also. Defaults to 1.

mold

Set cell mold speed. If set, a dead cell will go from death_color to
mold_color with a step of mold. mold can have a
value from 0 to 255.

life_color

Set the color of living (or new born) cells.

death_color

Set the color of dead cells. If mold is set, this is the first color
used to represent a dead cell.

mold_color

Set mold color, for definitely dead and moldy cells.

For the syntax of these 3 color options, check the "Color" section in the
ffmpeg-utils manual.

The haldclutsrc source provides an identity Hald CLUT. See also
haldclut filter.

The nullsrc source returns unprocessed video frames. It is
mainly useful to be employed in analysis / debugging tools, or as the
source for filters which ignore the input data.

The rgbtestsrc source generates an RGB test pattern useful for
detecting RGB vs BGR issues. You should see a red, green and blue
stripe from top to bottom.

The smptebars source generates a color bars pattern, based on
the SMPTE Engineering Guideline EG 1-1990.

The smptehdbars source generates a color bars pattern, based on
the SMPTE RP 219-2002.

The testsrc source generates a test video pattern, showing a
color pattern, a scrolling gradient and a timestamp. This is mainly
intended for testing purposes.

The testsrc2 source is similar to testsrc, but supports more
pixel formats instead of just rgb24. This allows using it as an
input for other tests without requiring a format conversion.

The yuvtestsrc source generates an YUV test pattern. You should
see a y, cb and cr stripe from top to bottom.

The sources accept the following parameters:

color, c

Specify the color of the source, only available in the color
source. For the syntax of this option, check the "Color" section in the
ffmpeg-utils manual.

level

Specify the level of the Hald CLUT, only available in the haldclutsrc
source. A level of N generates a picture of N*N*N by N*N*N
pixels to be used as identity matrix for 3D lookup tables. Each component is
coded on a 1/(N*N) scale.

Specify the frame rate of the sourced video, as the number of frames
generated per second. It has to be a string in the format
frame_rate_num/frame_rate_den, an integer number, a floating point
number or a valid video frame rate abbreviation. The default value is
"25".

Set color which will be used for drawing median phase. If color is
none which is default, no median phase value will be drawn.

The filter also exports the frame metadata lavfi.aphasemeter.phase which
represents mean phase of current audio frame. Value is in range [-1, 1].
The -1 means left and right channels are completely out of phase and
1 means channels are in phase.

The filter is used to measure the difference between channels of stereo
audio stream. A monoaural signal, consisting of identical left and right
signal, results in straight vertical line. Any stereo separation is visible
as a deviation from this line, creating a Lissajous figure.
If the straight (or deviation from it) but horizontal line appears this
indicates that the left and right channels are out of phase.

Get the current time, set it as frame metadata (using the key
lavfi.bench.start_time), and forward the frame to the next filter.

‘stop’

Get the current time and fetch the lavfi.bench.start_time metadata from
the input frame metadata to get the time difference. Time difference, average,
maximum and minimum time (respectively t, avg, max and
min) are then printed. The timestamps are expressed in seconds.

Concatenate audio and video streams, joining them together one after the
other.

The filter works on segments of synchronized video and audio streams. All
segments must have the same number of streams of each type, and that will
also be the number of streams at output.

The filter accepts the following options:

n

Set the number of segments. Default is 2.

v

Set the number of output video streams, that is also the number of video
streams in each segment. Default is 1.

a

Set the number of output audio streams, that is also the number of audio
streams in each segment. Default is 0.

unsafe

Activate unsafe mode: do not fail if segments have a different format.

The filter has v+a outputs: first v video outputs, then
a audio outputs.

There are nx(v+a) inputs: first the inputs for the first
segment, in the same order as the outputs, then the inputs for the second
segment, etc.

Related streams do not always have exactly the same duration, for various
reasons including codec frame size or sloppy authoring. For that reason,
related synchronized streams (e.g. a video and its audio track) should be
concatenated at once. The concat filter will use the duration of the longest
stream in each segment (except the last one), and if necessary pad shorter
audio streams with silence.

For this filter to work correctly, all segments must start at timestamp 0.

All corresponding streams must have the same parameters in all segments; the
filtering system will automatically select a common pixel format for video
streams, and a common sample format, sample rate and channel layout for
audio streams, but other settings, such as resolution, must be converted
explicitly by the user.

Different frame rates are acceptable but will result in variable frame rate
at output; be sure to configure the output file to handle it.

EBU R128 scanner filter. This filter takes an audio stream as input and outputs
it unchanged. By default, it logs a message at a frequency of 10Hz with the
Momentary loudness (identified by M), Short-term loudness (S),
Integrated loudness (I) and Loudness Range (LRA).

The filter also has a video output (see the video option) with a real
time graph to observe the loudness evolution. The graphic contains the logged
message mentioned above, so it is not printed anymore when this option is set,
unless the verbose logging is set. The main graphing area contains the
short-term loudness (3 seconds of analysis), and the gauge on the right is for
the momentary loudness (400 milliseconds).

Set the EBU scale meter. Default is 9. Common values are 9 and
18, respectively for EBU scale meter +9 and EBU scale meter +18. Any
other integer value between this range is allowed.

metadata

Set metadata injection. If set to 1, the audio input will be segmented
into 100ms output frames, each of them containing various loudness information
in metadata. All the metadata keys are prefixed with lavfi.r128..

Default is 0.

framelog

Force the frame logging level.

Available values are:

‘info’

information logging level

‘verbose’

verbose logging level

By default, the logging level is set to info. If the video or
the metadata options are set, it switches to verbose.

peak

Set peak mode(s).

Available modes can be cumulated (the option is a flag type). Possible
values are:

‘none’

Disable any peak mode (default).

‘sample’

Enable sample-peak mode.

Simple peak mode looking for the higher sample value. It logs a message
for sample-peak (identified by SPK).

‘true’

Enable true-peak mode.

If enabled, the peak lookup is done on an over-sampled version of the input
stream for better peak accuracy. It logs a message for true-peak.
(identified by TPK) and true-peak per frame (identified by FTPK).
This mode requires a build with libswresample.

dualmono

Treat mono input files as "dual mono". If a mono file is intended for playback
on a stereo system, its EBU R128 measurement will be perceptually incorrect.
If set to true, this option will compensate for this effect.
Multi-channel input files are not affected by this option.

panlaw

Set a specific pan law to be used for the measurement of dual mono files.
This parameter is optional, and has a default value of -3.01dB.

In order to submit one frame to output, these filters need to enqueue
at least one frame for each input, so they cannot work in case one
input is not yet terminated and will not receive incoming frames.

For example consider the case when one input is a select filter
which always drops input frames. The interleave filter will keep
reading from that input, but it will never be able to send new frames
to output until the input sends an end-of-stream signal.

Also, depending on inputs synchronization, the filters will drop
frames in case one input receives more frames than the other ones, and
the queue is already filled.

If both value and key is set, select frames
which have such metadata. If only key is set, select
every frame that has such key in metadata.

‘add’

Add new metadata key and value. If key is already available
do nothing.

‘modify’

Modify value of already present key.

‘delete’

If value is set, delete only keys that have such value.
Otherwise, delete key. If key is not set, delete all metadata values in
the frame.

‘print’

Print key and its value if metadata was found. If key is not set print all
metadata values available in frame.

key

Set key used with all modes. Must be set for all modes except print and delete.

value

Set metadata value which will be used. This option is mandatory for
modify and add mode.

function

Which function to use when comparing metadata value and value.

Can be one of following:

‘same_str’

Values are interpreted as strings, returns true if metadata value is same as value.

‘starts_with’

Values are interpreted as strings, returns true if metadata value starts with
the value option string.

‘less’

Values are interpreted as floats, returns true if metadata value is less than value.

‘equal’

Values are interpreted as floats, returns true if value is equal with metadata value.

‘greater’

Values are interpreted as floats, returns true if metadata value is greater than value.

‘expr’

Values are interpreted as floats, returns true if expression from option expr
evaluates to true.

expr

Set expression which is used when function is set to expr.
The expression is evaluated through the eval API and can contain the following
constants:

VALUE1

Float representation of value from metadata key.

VALUE2

Float representation of value as supplied by user in value option.

file

If specified in print mode, output is written to the named file. Instead of
plain filename any writable url can be specified. Filename “-” is a shorthand
for standard output. If file option is not set, output is written to the log
with AV_LOG_INFO loglevel.

These filters are mainly aimed at developers to test direct path in the
following filter in the filtergraph.

The filters accept the following options:

mode

Select the permissions mode.

It accepts the following values:

‘none’

Do nothing. This is the default.

‘ro’

Set all the output frames read-only.

‘rw’

Set all the output frames directly writable.

‘toggle’

Make the frame read-only if writable, and writable if read-only.

‘random’

Set each output frame read-only or writable randomly.

seed

Set the seed for the random mode, must be an integer included between
0 and UINT32_MAX. If not specified, or if explicitly set to
-1, the filter will try to use a good random seed on a best effort
basis.

Note: in case of auto-inserted filter between the permission filter and the
following one, the permission might not be received as expected in that
following filter. Inserting a format or aformat filter before the
perms/aperms filter can avoid this problem.

The PTS of the filtered video frame,
expressed in seconds. It’s NAN if undefined.

prev_pts

The PTS of the previously filtered video frame. It’s NAN if undefined.

prev_selected_pts

The PTS of the last previously filtered video frame. It’s NAN if undefined.

prev_selected_t

The PTS of the last previously selected video frame. It’s NAN if undefined.

start_pts

The PTS of the first video frame in the video. It’s NAN if undefined.

start_t

The time of the first video frame in the video. It’s NAN if undefined.

pict_type (video only)

The type of the filtered frame. It can assume one of the following
values:

I

P

B

S

SI

SP

BI

interlace_type (video only)

The frame interlace type. It can assume one of the following values:

PROGRESSIVE

The frame is progressive (not interlaced).

TOPFIRST

The frame is top-field-first.

BOTTOMFIRST

The frame is bottom-field-first.

consumed_sample_n (audio only)

the number of selected samples before the current frame

samples_n (audio only)

the number of samples in the current frame

sample_rate (audio only)

the input sample rate

key

This is 1 if the filtered frame is a key-frame, 0 otherwise.

pos

the position in the file of the filtered frame, -1 if the information
is not available (e.g. for synthetic video)

scene (video only)

value between 0 and 1 to indicate a new scene; a low value reflects a low
probability for the current frame to introduce a new scene, while a higher
value means the current frame is more likely to be one (see the example below)

concatdec_select

The concat demuxer can select only part of a concat input file by setting an
inpoint and an outpoint, but the output packets may not be entirely contained
in the selected interval. By using this variable, it is possible to skip frames
generated by the concat demuxer which are not exactly contained in the selected
interval.

This works by comparing the frame pts against the lavf.concat.start_time
and the lavf.concat.duration packet metadata values which are also
present in the decoded frames.

The concatdec_select variable is -1 if the frame pts is at least
start_time and either the duration metadata is missing or the frame pts is less
than start_time + duration, 0 otherwise, and NaN if the start_time metadata is
missing.

That basically means that an input frame is selected if its pts is within the
interval set by the concat demuxer.

A commands description consists of a sequence of interval
specifications, comprising a list of commands to be executed when a
particular event related to that interval occurs. The occurring event
is typically the current frame time entering or leaving a given time
interval.

An interval is specified by the following syntax:

START[-END] COMMANDS;

The time interval is specified by the START and END times.
END is optional and defaults to the maximum time.

The current frame time is considered within the specified interval if
it is included in the interval [START, END), that is when
the time is greater or equal to START and is lesser than
END.

COMMANDS consists of a sequence of one or more command
specifications, separated by ",", relating to that interval. The
syntax of a command specification is given by:

[FLAGS] TARGETCOMMANDARG

FLAGS is optional and specifies the type of events relating to
the time interval which enable sending the specified command, and must
be a non-null sequence of identifier flags separated by "+" or "|" and
enclosed between "[" and "]".

The following flags are recognized:

enter

The command is sent when the current frame timestamp enters the
specified interval. In other words, the command is sent when the
previous frame timestamp was not in the given interval, and the
current is.

leave

The command is sent when the current frame timestamp leaves the
specified interval. In other words, the command is sent when the
previous frame timestamp was in the given interval, and the
current is not.

If FLAGS is not specified, a default value of [enter] is
assumed.

TARGET specifies the target of the command, usually the name of
the filter class or a specific filter instance name.

COMMAND specifies the name of the command for the target filter.

ARG is optional and specifies the optional list of argument for
the given COMMAND.

Between one interval specification and another, whitespaces, or
sequences of characters starting with # until the end of line,
are ignored and can be used to annotate comments.

A simplified BNF description of the commands specification syntax
follows:

Set the timebase to use for the output frames timestamps.
It is mainly useful for testing timebase configuration.

It accepts the following parameters:

expr, tb

The expression which is evaluated into the output timebase.

The value for tb is an arithmetic expression representing a
rational. The expression can contain the constants "AVTB" (the default
timebase), "intb" (the input timebase) and "sr" (the sample rate,
audio only). Default value is "intb".

Specify the transform timeclamp. At low frequency, there is trade-off between
accuracy in time domain and frequency domain. If timeclamp is lower,
event in time domain is represented more accurately (such as fast bass drum),
otherwise event in frequency domain is represented more accurately
(such as bass guitar). Acceptable range is [0.1, 1]. Default value is 0.17.

Specify the transform count for every single pixel. Default value is 0,
which makes it computed automatically. Acceptable range is [0, 10].

fontfile

Specify font file for use with freetype to draw the axis. If not specified,
use embedded font. Note that drawing with font file or embedded font is not
implemented with custom basefreq and endfreq, use axisfile
option instead.

font

Specify fontconfig pattern. This has lower priority than fontfile.
The : in the pattern may be replaced by | to avoid unnecessary escaping.

fontcolor

Specify font color expression. This is arithmetic expression that should return
integer value 0xRRGGBB. It can contain variables:

Set the number of samples which are printed on the same column. A
larger value will decrease the frame rate. Must be a positive
integer. This option can be set only if the value for rate
is not explicitly specified.

rate, r

Set the (approximate) output frame rate. This is done by setting the
option n. Default value is "25".

split_channels

Set if channels should be drawn separately or overlap. Default value is 0.

colors

Set colors separated by ’|’ which are going to be used for drawing of each channel.

Delete side data of type. If type is not set, delete all side
data in the frame.

type

Set side data type used with all modes. Must be set for select mode. For
the list of frame side data types, refer to the AVFrameSideDataType enum
in libavutil/frame.h. For example, to choose
AV_FRAME_DATA_PANSCAN side data, you must specify PANSCAN.

Sythesize audio from 2 input video spectrums, first input stream represents
magnitude across time and second represents phase across time.
The filter will transform from frequency domain as displayed in videos back
to time domain as presented in audio output.

This filter is primarily created for reversing processed showspectrum
filter outputs, but can synthesize sound from other spectrograms too.
But in such case results are going to be poor if the phase data is not
available, because in such cases phase data need to be recreated, usually
its just recreated from random noise.
For best results use gray only output (channel color mode in
showspectrum filter) and log scale for magnitude video and
lin scale for phase video. To produce phase, for 2nd video, use
data option. Inputs videos should generally use fullframe
slide mode as that saves resources needed for decoding video.

The filter accepts the following options:

sample_rate

Specify sample rate of output audio, the sample rate of audio from which
spectrum was generated may differ.

channels

Set number of channels represented in input video spectrums.

scale

Set scale which was used when generating magnitude input spectrum.
Can be lin or log. Default is log.

slide

Set slide which was used when generating inputs spectrums.
Can be replace, scroll, fullframe or rscroll.
Default is fullframe.

win_func

Set window function used for resynthesis.

overlap

Set window overlap. In range [0, 1]. Default is 1,
which means optimal overlap for selected window function will be picked.

orientation

Set orientation of input videos. Can be vertical or horizontal.
Default is vertical.

The name of the resource to read (not necessarily a file; it can also be a
device or a stream accessed through some protocol).

format_name, f

Specifies the format assumed for the movie to read, and can be either
the name of a container or an input device. If not specified, the
format is guessed from movie_name or by probing.

seek_point, sp

Specifies the seek point in seconds. The frames will be output
starting from this seek point. The parameter is evaluated with
av_strtod, so the numerical value may be suffixed by an IS
postfix. The default value is "0".

streams, s

Specifies the streams to read. Several streams can be specified,
separated by "+". The source will then have as many outputs, in the
same order. The syntax is explained in the “Stream specifiers”
section in the ffmpeg manual. Two special names, "dv" and "da" specify
respectively the default (best suited) video and audio stream. Default
is "dv", or "da" if the filter is called as "amovie".

stream_index, si

Specifies the index of the video stream to read. If the value is -1,
the most suitable video stream will be automatically selected. The default
value is "-1". Deprecated. If the filter is called "amovie", it will select
audio instead of video.

loop

Specifies how many times to read the stream in sequence.
If the value is less than 1, the stream will be read again and again.
Default value is "1".

Note that when the movie is looped the source timestamps are not
changed, so it will generate non monotonically increasing timestamps.

discontinuity

Specifies the time difference between frames above which the point is
considered a timestamp discontinuity which is removed by adjusting the later
timestamps.

It allows overlaying a second video on top of the main input of
a filtergraph, as shown in this graph:

For details about the authorship, see the Git history of the project
(git://source.ffmpeg.org/ffmpeg), e.g. by typing the command
git log in the FFmpeg source directory, or browsing the
online repository at http://source.ffmpeg.org.

Maintainers for the specific components are listed in the file
MAINTAINERS in the source code tree.